Lots of great advice!
If you have power, you can keep an on board or even a beside the slip refrigerator stocked.
On boards are nice, but the size is limited. A moderate 4-6 or larger cf mini-fridge/freezer can keep your frequently used beverages, ice, condiments, frozen food items, and a lot more on hand so you don't have to take everything off-board, home, and return every trip. A good hasp and padlock helps keep sea lions, otters, casual human moochers, and other bandits out of your treasure chest. Get a very well sealed container and plastic bags, and you can add in frozen bait, if your Fleet Admiral doesn't read you The United States Official Marine Riot Act and stick your copy of Chapman's between your cheeks......!
I second Greg's ideas about the slip, and have done them all, plus a lot more. Just use your imagination to customize the slip to your needs within the marina's limits. I like to make the boat and slip a custom cabin/home away from home to retreat to. It gets so hot here in Redding, that staying under a covered slip during the mid-day summer sun is a lot smarter than running around, burning up fossil fuels in the sun. The fishing is better under the docks, too!
Check to see if the marina requires you to present your boat registration, insurance, and/or other documentation. Our contract says that the marina wants you to indemnify them against any loss caused by your actions or negligence, etc., but I don't think they really can or could enforce it.
What's the crime record in the marina? Boats broken into? Rare here, but it has happened. Most thefts in a marina are typically "crimes of opportunity"- something just left unlocked, out in the open, too easy, etc. One of the marinas has the Shasta Lake Sherriff's Detail housed in it, and that helps a lot.
Does the marina have a fireboat and proactive fire prevention policies, etc? It only takes one fool, etc. The "Careless BBQ to Bonfire of the Boating World" in 10 minutes or less is an all too often News at 11 story. (Reported on this site about twice a year.)
Curious note: I didn't know it at first, but after about a month or two I found I had a nesting family of River Otters in the styrofoam flotation part of dock right next to my boat. I'd already seen their scats on the dock, and knew they at least visited, but one day while sitting in a chair on the dock and working on my anchor rode, one popped up out of the water, right within reach, and stopped to look at me. Fortunately, I resisted the initial urge to pet the 'kitty'. Well, that's my story and I've still got the fingers to prove it! :wink So far, the marina hasn't put an additional charge on my monthly bill for entertainment.
Which brings us to the cost factor. You might be surprised to figure out how much that slip will cost over the years. We've kept two slips rented at a combined cost about $550/mo for over 10 years which comes to over $60,000. But it's fun and we can afford it, so why worry? Just be sure your use and pleasure justifies the eventual cost. However, on a personal note, I'm getting to the age where boat upkeep and use are a real chore, so we'll be putting a boat of two up for sale later this coming Spring.
This topic never ends, but that's all for now!
Joe. :teeth :thup