Remove the Removables
Take the battery inside and, if possible, store it on a slab of wood (cold concrete on a garage floor can be the same as leaving it on the boat outside). If electronics can be removed, do so. If you keep registration information onboard, take it inside for the winter.

Inspect the Inspectables
This is the right time to take a look at expiration dates of flares as well as the charging status of the fire extinguisher. It is always better to discover out of date equipment when at home on land than when you need them or when the Coast Guard has just come alongside while on the water asking to do an inspection. While you are in this mode, bring the first aid kit inside and replace bandages that may have become wet or medical supplies that have expired.

The Engine
Books have been written about how to winterize an engine. If it is an outboard, this is the time to change the lower unit oil. If you can run the engine using the garden hose as a water intake, fog the carburetor so that engine parts are coated with protecting oil. It is here where the four most common mistakes are made when the job is to winterize a boat-and some of these may not apply to your particular boat:

1. The engine block isn't drained
2. The Sea Strainer isn't drained
3. Seacocks or gate valves aren't closed
4. Petcocks that are used to drain water from the engine aren't inspected for possible clogging (Source the BoatUS Marine Insurance Division). If it is at all possible, take the outboard off the boat and store it in an upright position in the garage.

Trailer Notes

1. If it is possible, take the wheels off and block the hubs so they sit off the ground.
2. Cover the hubs with a few thorough wraps of plastic so that moisture is kept out of the bearings and brakes.
3. Take the tires inside or cover them if they will remain on the trailer (this is done because tires will begin the process called dry rot when sitting unused for long periods of time and the sun will harm a tire as well).
4. Don't park the boat (and trailer) under a tree because tree limbs and leaves fall during the winter. In one case, you have a mess to clean up and in another case, you have a bigger mess to clean up. In both cases, it is something that can usually be avoided.
5. Check the trailer from time to time. Do a walk-a-round and make sure nothing has shifted during the layover. This is especially important to do if your boat and trailer are stored at a marina or another area that is away from your line of sight.