Loosen the tappets so all the valves are closed. Fill the combusion chambers full of oil. Fill the crankcase as full as you can get it. Same with the transmission and final drive.
The idea is that, all of these components being open to air, will also be open to moisture. With oil completely filling them, there will be no free air space for that to happen.
Wash and wax the bodywork and frame - all the painted surfaces.
Empty the gas tank and carbs and leave the petcocks open.
Hit all the plastics and seat with plastic renewer.