Personally, I'd go through the whole boat and take everything off of it. Empty out all the lockers, cubbies, drawers, etc. and give everything on and now off the boat a basic clean. This process will give you an idea of what you have and where everything is (or was) on your boat. Make notes of were systems are located. Look for corrosion, wear and tear, and damage. Open an close valves. Turn stuff on and off to see if it works (for anything complex look at the owners manual first). Write down manufacturers and model numbers, take lots of pictures of anything and everything so you can reference stuff when you are away from the boat.
For all the stuff you took off the boat, spend some time to figure out what it is or what it does before you decide what to do with it. Some of it will have value to you, some of it will have value to someone else, some or maybe all of it will be junk. Only put stuff back on the boat once you decide that it needs to be there. Sell, donate, recycle, or toss the rest. (I'm bad at this part and still have a lot of random stuff stored under my basement stairs) Make sure you have a good set of the USCG or state required safety gear. Don't assume the stuff that came with the boat is still good, inspect or replace.
I agree with the others with the suggestions to do basic mechanical maintenance so you know the boat has a good starting point. Take lots of notes and start making to-do lists and note when you replaced things so you can start building a maintenance log for yourself (and probably the next guy) Start putting things in order of precedence with safety at the top and nice to have at the bottom.
A lot of stuff, like standing rigging for example, will depend a lot on what previous owners have done. If it was replaced a couple years ago, it's probably fine and should just be inspected for damage or wear, but if it's original, you should probably consider replacing it soon.
Good luck and have fun.