Been there, doing this... our boat is 800 miles away for the foreseeable future.
Good advice already posted, what I would add:
1) Pick a marina with locked gates... not perfect but helps a lot
2) Give your name and contact info out to the boats around your slip... leave a note in a zip lock on their deck
if they're not around so they get it next time they're there.
3) Post a large note in an easily visible portlight on the slip side of your boat with your contact information and the port's contact information... that way if there's a problem hopefully someone will call you and if you don't answer they can at least call the port (lots of people don't seem to know their port's number).
4) High water alarm
... put the switch for a very loud alarm
slightly above the switch for your bilge pump... the note in our window is very explicit "If you hear the alarm ringing, this boat is flooding and trying to sink... please call us or the port".
5) If you meet someone who at least will be walking by your boat a lot, consider turning on a 110v light and leaving it on... that way if they walk by your boat and see that the 110 light isn't burning they know shore power
has gone out to your boat for some reason (which theoretically leaves you vulnerable because your bilge pump might run out of battery power eventually).
6) Chafe gear
on all your dock lines... old garden hose works great.
7) Close all through hulls (put put signs places that remind you they're closed before you try to fire up the engine or something... and obviously if you run a dehumidifier to your sink drain maybe leave that one open!).
8) Take lots of pictures of everything... partially for insurance
reasons and partially because you're always going to be trying to remember how some particular part of the boat looks / works / is set up.
9) Check in yellow pages or ask at port about yacht management companies... they can come check on your boat and do whatever else you might want.
10) If, like me, you're tired of your current
job, if #7 fails, move to that area and start a yacht management company