Well like many other things there are a 1000 different opinions.
For my vehicles that I store (including lawnmowers, tractors) I do the following:
1) Change all the fluids, drain and put in fresh.
- Coolant (unless it's real fresh)
- Tranny oil / crank case oil.
This sets me up for the next year ready to go.
2) Gas
- on 4 stroke machines I fill them to reduce the air in the tank, add some Sta-bil or other preservative and a splash of carb cleaner (i.e Gumout)
- 2 strokes, run it, shut the gas off, run the gas out of the carb, then drain the tank. I read somewhere that pre-mix and sta-bil don't get along that well.
3) Lube everything that can be lubed (chain, cables, etc.)
Winter time is a good time to strip it down and replace the bearings (wheels, frame, etc).
-MD