Basically, if it is going to be warm and dry, like in the living area of your house, then it is best to drain it (no need of having 4 gallons of highly flammable substance in your bedroom). Gasoline will tend to create that sticky varnish most rapidly in a warm environment, so if it is going in the house, drain it dry (and the carbs too). If it going to be in a cool and/or moist environment, the best thing that I have found is to put in about 2X the recommended dosage of STA-BIL and fill the tank right up. I then run the bike to make sure the STAB-IL/gas mixture is all through the carbs, and then I drain the bowls on the carbs. This way, if there is any fuel stuck in some little passageways in the carbs, at least it has STABIL in it and won't likely turn to glue over the winter months. The full tank prevents the inside of the tank from rusting (no place for cold wet air to start attacking bare steel).. It wouldn't hurt to put some "HEET" or isopropyl alcohol in the tank to help absorb water, though the higher levels of corn-squeezins we all have in our tanks these days will probably take care of that anyways.
I found that when I put my bikes in a heated cellar but didn't put the STABIL in the fuel, it was a coin toss whether or not I'd have a gunked up carb by the springtime. But, if the bikes were in my cold (basically unheated) garage, they would generally do OK. I got used to using STAB-BIL religiously every winter, so I continue to do so.
Of course, don't forget to turn your fuel petcock(s) OFF for the winter !
