Here is some reading material for you.
http://www.fuel-testers.com/review_g..._products.html
Personally I store over Winter with the tank full, with Stabil Marine in it, and ethanol free from a Station here in town that sells only ethanol free. I turn off the fuel shutoff, run the carb dry, empty the sediment bulb, and drain the carb. Run ethanol free during driving season with 2-3 oz. of Marvel Mystery oil per tankful.