Re: drain gas
Don't drain the gas out of the tank. That's exactly the opposite of what you want to do.
Add some Sta-bil or other products of your choice and
fill it. Then run the engine for a bit so the gas with the stabilizer gets into the fuel system and your good to go.
An empty tank will condensate and you have water in it next year. That's just never a good thing.
There are thread on here about how to winterize. Do a little reading and I think you can find some very useful information. Here is a link
Winterizing your engine and drive.