With my outboard, I just make sure I stabilize the fuel and run it long enough to make sure that the stabilizer makes it through the engine. Take the battery out, charge it up to the max and then store it in a warm place. I've never fogged it in the 15 years I've had it and never had a problem. In the spring, I just pull the plugs, squirt some oil in, turn it over a few times by hand, put the plugs back in and fire it up. I generally do the same with my inboard, except that I do fog the engine. Both boats stored in unheated locations, the IB at the coast and the OB in the interior.
Like mountainman mentioned, I keep the built-in tanks full and lube all grease-points. The day-tanks I don't worry about as much. Usually (when I remember anyway) crank the steering controls over so that none of the cylinders are exposed to the air.
It's a good time to go over the trailer too. Check bearings, wiring etc.
All pretty easy stuff to do, especially when you see what some of the shops will charge you to do the same.