The search for the perfect liveaboard marina is best done in parallel with your boat search.  Looking for boats will take you to several different locations.  This is a great chance to scout the marina in that area as well.  I recommend finding a marina before closing on any boat.  Reason being, what if you purchase your perfect liveaboard boat only to find that there's no slips available at a liveaboard friendly marina.  Or purchase a sailboat without any local slips having You won't be completely screwed but it's not going to be a plus.  

Starting out, the biggest thing, I think you'll agree, is the location.  If you're still a wage slave like myself you'll need to consider your commute.  This is especially true for those of us in major metropolitan areas.  Living on a boat is amazing but driving a hour and a half one way to work will eventually make you salty (not in a good way) about the whole thing.  That'll go double in wintertime.   Luckily there is usually navigable waters in most large cities.  And this means marinas will be available.   

Next and also paramount is; Does the marina except liveaboards?  Most of them don't advertise that they do.  And it can be a ticky question to ask.  Not in the sense of hard to say but that it can put you in a predicament.  ie,  Let's say you did purchase a boat and found the perfect liveaboard marina.  But, maybe didn't clarify availability during your scouting visit.  When you go to sign a slip lease the dock master tells you that you're all set but it's just that there's a three-six month wait until your slip opens up.  Uh-oh.  Here's were the predicament can emerge.  The other marina in the area has open slips but told you "absolutely no liveaboards"!  You found this out three weeks earlier when you were there speaking with the dock master.  When you asked if you could be a liveaboard,  she shewed you out the door with a broom.   Now that you've purchased a boat, you have to park it somewhere, you've already gave notice on your apartment, and you're not going to have a place to stay.   Being sly you head over and get a slip anyway.  Thinking you could probably avoid being detected as a liveaboard if you limit your comings and goings.  The dock master recognizes you, signs you up while giving you the hairy eyeball, and she makes a point to clarify that this is a no liveaboard marina.  You take the short term lease anyway. I mean, what are you going to do, you don't have much of a choice? You get your boat there and everything seems to be working out.  You've managed to not draw attention to yourself.  About a month later the dock master asks you if you're living aboard because they've seen you here a lot and you say no, that you just have a lot of repair work going on and you often stay over because it's easier than going home.  A month or so later she approaches you and says we've counted your car in the parking lot every night for the last month and your in violation of your slipholder agreement.   You need to remove your boat and you forfeit the rest of your lease money.  Later you'll realize that you may have gotten away with it if you hadn't originally gone into the office asking about being a liveaboard.  Now, this is an extreme example.  The dock master at most marinas isn't out to cause problems and if you had a short term lease on a slip they'd figure that you just needed a temporary slip to stay at until your other slip was ready.  As I mentioned in "financing a boat, what to expect" play your intentions of being a liveaboard close to your chest.  Just to avoid closing doors and awkward situations.  It may be best to call a perspective marina an ask the liveaboard question anonymously before your visit.

There are methods and tricks to being a "sneak-aboard" and living on the hook but they merit their own article. So, going with the assumption that every marina you're looking at is liveaboard friendly and within your commuting range.  Here's what you'll want to look for in a perspective marina.

Facilities, what you need in the basics. 

1. Parking, seems simple, just remember that you have to walk from your car to not just the dock but also out the dock.  Those steps can add up.  Especially, if the marina doesn't have dock carts for everyone's use.  Remember too, that it's not always going to be sunny and 80 degrees.  A 200 yard walk out a frozen dock can test your metal.  
2. Type of dock.  Is it a floating dock or on pilings.  Is it concrete, wood, synthetic wood?  All have advantages and disadvantages depending out your boat. Whats the condition? Is it a scary swaying walk with cracking deck boards or do you feel you could ride your bike down the dock at full speed without a care.
3. Water.  Does the marina have city water? Well water? Water at the slip? City water pressure can be so high that it damages the pipes in your boat potentially sinking you.  Well water can be dirty, contaminated, full of iron or sulfur.  This too can damage your boat's inner workings.  What water service is provided during the winter?  If they turn off the water completely, what then, do they have a frost free spigot to access?
4. Electricity.  A must have to run your boat.  You need to know what electrical services are available?  30amp, 50amp, 100amp?  Not only for the slip but for your boat.  There may be an open slip but it might not be compatible with your boat's electrical system.  Running your generator is an option but not a good one.  It will require fuel and maintenance, is noisy and can be smelly. There is always the option of purchasing a power adapter provided that the electrical hook up can handle your needs.  Doesn't hurt to ask if they have any kind of grounding protection to help guard against electrolysis either. 
5. Bathrooms and showers.  At a bare bones minimum they need to have a basic half bathroom available 24/7.  Checking out the bathroom is the best gauge of any marina.  If the bathroom is neglected and out of date, everything else in the marina will follow.  Showers are the same.  There are some marinas that have a locker room style shower set up still.  I'd recommend against that unless it doesn't bother you to look at wrinkly ass cheeks everyday. Of course that may save you from buying coffee in the mornings. 
6. Ice machine.  Doesn't seem like much but you're going to use the hell out of this.  Make sure it's in good working order or its a bag service.  Even if your boat is equipped with an ice maker.  It's going to either be broken (I swear all ice makers come broken from the factory) or not big enough for your needs.
7. Waste pump out.  Again, at a bare minimum there needs to be one in the marina.  If you have to move the boat to get to it, you're not going to be happy.  Some marinas have portable units that can be rolled down the dock. This isn't optimal but it's better than moving the boat.
8. Depth of the water.  Another basic requirement: Does your boat's draft (lowest point below the water) fit in the marina?  Marinas tend to silt up over time and require dredging.  Ask when the last time this was done to your perspective slip. You don't want to end up in the mud at low tide.

Amenities, what you want.

1. Hotel style bathrooms.  Sink, mirror, bench, toilet & shower in one room to yourself. Goes without saying it's better than a room with stalls.  
2. Common room.  Basically a lounge with table and chairs.  Maybe a sharing library, television, or a kitchenette.  A nice place to hang out if you need too. 
3. Vending machines.  Drinks, coffee, sandwiches, and/or toiletries. God knows you don't want to eat anything out of these on a long term basis but they're nice to have around if you need them.
4. Trash service.  Just because you downsized doesn't mean your trash production will.  A full garbage bag can stink up a boat in minutes and it can take up as much room as a person.  Leaving it on deck to take to out in the morning isn't a good idea with all the critters around.  You want to be able to take the garbage out to a dumpster immediately.
5. Gas Grill. Most marinas forbid using an on board grill for safety reasons.  But as a concession they'll provide one. It's a good way to meet your neighbors and make friends and still feel like you have a little yard space.
6. Game room,  a pool table, foosball, or video games is nice when company with kids comes over or you need a distraction.
7. Laundry room.  Even if you plan to do laundry at a local laundromat having one at the marina can be nice.
8. Gazebo. This goes hand in hand with the gas grill.  It's where all the liveaboards will gather for drinks and BSing.  
9. Lawn space.  Especially true if you have a dog with you.  Having a little patch of grass is a plus.
10. Pump out service.  It's a nice thing to have some one else clean your holding tank.
11. Dock carts.  Mentioned above, these are marina equivalents of a shopping cart.  You'll be very happy to have access to one when bringing in the groceries or laundry down a 150 yard dock. 
12. High speed internet, If you want to stream services like Netflix, Amazon, or Hulu you need not only a good ISP at the marina but a strong wifi network.  A sign that you won't be able to rely on the marina internet is if the office has an old linksys router on a shelf and the login password is "password".  Both are sure signs you won't be getting good service.  You want to see WiFi stations on the docks themselves.  This is usually a good sign that the marina has taken the time to invest in quality internet service.
13. Cellar signal strength.  This isn't on the marina but it's important to be able to have access to your phone services and not be in a dead spot.  Check your signal strength when you go there for the first time.

Resort level amenities that make it nice for you.

1. Pool.  The pool is where you go to cool off because you don't want to swim in the marina water.  Check out the pool, is it nice or something they just threw in to check an amenities box on Dockwa
2. Hot tub, a great thing to have after your long day of your boat beating you up. Boats bite people make no mistake.  You always have to watch for this.
3. Sauna, a bit on the rare side but they're out there.  Nice in the winter for adjusting your core temperature the way the Fins do.
4. Pool side bar, inevitably the drink you brought from the boat to the pool is going to run out. At the ready refills are a big plus.
5. Fire Pit, great gathering spot and hang out
6. Dog walk
7. Events,  lots of nicer marinas are going to hold slipholder events with food, drink and music
8. Workout gym,  not something you want to use but you probably need it.
9. Services.  Detailing, Cleaning, Stocking (There are services that will stock your boat with supplies, expensive but nice)
10. Storage buildings.  Rental storage in the marina will give you a place to keep seasonal items, tools, and personal effects that you'd like to keep.  You can always find one of these close by but if you can walk to it, it's much better.
11. Loaner SUPs, kayaks, yard games and/or bikes.  All nice to have access to and not have to purchase.
12. A "good" dockside bar & restaurant.  It's nice to be able to go grab a bite on project day instead of stopping everything to cook.  Or to get Sunday morning breakfast with your spouse.  A dinghy dock at the restaurant is an added bonus.  Then you can take the dinghy to go eat.

Amenities you'll want for your boat.

1. Again, pump out service.  I can't stress this enough, you'll be happy that you looked into this thoroughly.
2. Fuel Dock,  Marinas that have a fuel dock are best for keeping you topped up.  If the fueling requires stopping somewhere else, the tendency will be to wait until the next trip to top up.  This is important to avoid because leaving an air gap in your fuel tank will cause condensation to form on the inside walls that are exposed to the air.  Much like a cold glass of water can do.  The condensation can be bad enough to drip down into the fuel.  Over time this accumulates in the bottom of the tank and will foul your fuel.  Potentially causing damage to your engines. 
3. Full length finger piers.  If you're new, a finger pier is the little part of the dock that runs out the side of the slip along your boat.  This makes cleaning and servicing your boat much easier.  Gives you view and boarding options because you can tie up in the slip either bow in or out.
4. Floating dock.  Because the dock floats on the water same as your boat, tying up is much easier.  You won't have to allow for tides and don't have have to aim for the center of the slip to avoid dock rubbing damage.  On a floating dock you can tie slam up against it with a handful of fenders between the dock and the boat. Thereby lessening the gap to the boat making boarding much easier and safer.  It takes away the "leap of faith" you sometimes get on a piling dock during extreme tides.  However, a floating dock isn't always best for a sailboat.  Sailboats will require a step up to reach the deck from the dock.
5. Covered slip.  This isn't a must but it's nice to have.  It will lessen the need for waxing, chances of water leaks, and the sun cooking the inside of your boat.  If a covered slip is available even though it will cost more.  Given the amount it will save you in maintenance, wear and tear, and electricity makes it worth the extra expense.  Again, this is a no go for Sailboats. The mast will prevent you from fitting under the roof of a covered slip.
6. Boat yard near by.  Having one at the marina adds an industrial feel to what you want to be residential feeling. If you're in close proximity to a yard it's a little nicer than being at one.  If the yard is far off and you have a problem that requires a tow it can get expensive.  
7. Dock boxes; A dock box is a large container that's attached to the dock at your slip for storing items.  It's a great thing to have for hoses, cleaning equipment, or other boating gear. You'll want all the storage you can get. 
8. Dinghy dock and dinghy racks.  A dinghy dock is small dock for launching and recovering dinghies, SUPs, or kayaks.  The rack is for storage of these if you don't have a davit or rack system on your boat.
9. Security.  Whether it's just a coded dock gate or a security guard.  Protecting your boat when you're not there is a must.  Boats have very little security built into them.  Any novice thief can board a boat and circumvent it's locker and door locks or even the ignition.  The best protection is not letting them a chance to get on board.  Say no to any marina that allows public access to the docks.  I see this at a lot of new or gentrified marinas.  They place the boats on show to attract the public for the benefit of the surrounding businesses.  This is usually done by property management groups that own the surrounding buildings.   They're not in the marina business.  They see your boat as a promotional tool and charge you for this privilege.  Pass.   

Amenities and signs of marinas you'll want to avoid if possible.

1. A marina with a launch or ramp for trailered boats.  When the first warm Saturday rolls around and you can't find parking because there are trucks with trailers everywhere.  The bathrooms are overflowing, there's no ice in the machine and it's nothing but engines revving and exhaust fumes.  You'll know why I recommended avoiding this.  Granted, it's great people watching.  You and your friends can play the sinking boat drinking game.  The rules are simple; you have to down your drink every time someone forgets to put the drain plug back in their boat before launching.  Shots all around if someone forgets to put on the parking brake and sinks their truck.  Boat ramp panic is pretty entertaining. 
2. Wave and wake action.  Trying to live on a boat that you can't leave a full cup of coffee on the counter without fear of it flying across the cabin is not going to be possible.  You need to know how protected the marina is from wave and wake action. First ask around, slip holders will tell you, the dock master might not.  Will there be fishing boats buzzing by every morning at 5 am? Is there a no wake zone in the waters around the marina?  Does the marina have a breakwater? Is the slip you're looking at have protection behind that breakwater?  Sit for a minute and watch the boats in the marina.  Watch for movement.  
3. Condition and age of the other boats in the marina.  If majority of the boats in the marina are old garbage scows chances are the marina isn't bringing in enough money to maintain the facilities or is being run by a cheap or incompetent owner.  Either way, you're going to get what you pay for.  So, if you find a slip with just a mast coming out of the water with seagull poop and barnacles all over it, it's a sure sign to move on.  
4. Presence of Jet Skis.  If your slip is within sight of people riding Jerk Skis, run.  The only people that like Jet skis on the water are the people riding them.  They're the unlicensed mini bike of the water.  Buzzing around and kicking up wakes like little kids at the pool.  They'll ruin your Saturday morning coffee.   If you own a jet ski you should think about your life choices.  
5. Public access,  I'll mention this again.  No, no, no to public access docks or bulkheads.  You may be able to find a "cool" slip downtown where the action is but that'll sour fast when drunks board your boat at 2am or bang on the hull asking for a glass of water (true story).  Even if it's a public access bulkhead with a private finger pier.  You'll be on guard non stop.  Not fun.

This should give you a general idea of what to look for in a marina.  I'm sure there's other things that should be on this list too.  But, this will get you started.  Leave a comment if there's something you'd like to add or have a question about.

Cheers

Mike

Life's a Port