Copied from various sites online

1. Fill your gas tank.
2. Buy gasoline antifreeze containing gasoline stabilizer; this will help maintain the gasoline’s combustible qualities over the winter.
3. Go for a 60 minute ride to get the fuel additive through your bikes fuel system (5 minutes would be more than enough, but heck, if you are putting the bike away for the winter you’ll want to go for one last ride).
4. Re-fill your tank to the top again on the way home.
5. Change your oil and oil filter, since old oil is corrosive. Rotate the engine a few times to circulate the fresh oil. The plugs will probably have to be removed but leave them in their caps AND grounded to prevent damage to the ignition system. Also, make sure that there is nothing flammable nearby, as the plugs will still be sparking! Re-install the plugs. If you are only storing the bike for one winter don’t bother putting any engine oil in the cylinders (fogging). For long periods of storage (a year or more) place a tablespoon of clean engine oil into each cylinder prior to rotating.
6. Spray a good amount of WD-40 or other water dispersant down the exhaust, and then cover with a plastic bag sealing with an elastic.
7. If possible, put a plastic bag over the air intake to prevent moisture buildup or even small rodents from making homes in your air filter box.
8. Lubricate all cables and joints with proper lube; avoid WD40 because it evaporates.
9. Check the cooling system (if your bike is liquid cooled). Check the level and top up if necessary. Better still, take this opportunity to change the coolant altogether. The coolant should be a 50/50 antifreeze/water mix.
10. Remove the battery and store it away from direct sunlight, in a warm area; batteries can freeze, causing them to crack and leak, which can cause extensive (and expensive) damage. Check your battery’s electrolyte level and top it up if necessary. Use only distilled water — and never top it up with acid! Trickle charge it every month at the required amp hour rating. A good way to do this is to hook up a timer to automatically charge the battery occasionally so you don’t have to remember to turn it on or off.
11. Drain your carbs and don’t refill them. Gas left in the carbs for extensive periods can turn into a varnish-like substance that will clog jets and stick floats.
12. Wash and dry the bike thoroughly. Wax painted areas and apply a thin layer of light oil or petroleum jelly to chrome and aluminum areas to prevent rusting.
13. Inflate the tires to the recommended pressures.
14. Raise the bike onto the centre stand and lift the front of the bike until the front wheel is off the ground. Support the frame with wooden blocks (concrete or cinder blocks can crack under weight and/or scratch the paint) thus ensuring that both wheels are off the ground. If your bike has a side stand only, move the bike around once a month or more to rotate the tires, thereby preventing flat spots.
15. Inside or outside, a cover is a good idea. Avoid plastic as it turns brittle with the cold and can rip, whip against painted areas and/or trap moisture underneath it (since it doesn’t breathe). A proper canvas bike cover (preferably with a tie cord and a lock) is always best.

Found this video on YouTube: