From cheapest to more expensive.
Fuel in small engines
1) Ethanol absorbs water from the air, and the water in turn will do damage to engines and fuel systems. For most small engines with vented gas tanks, store them with the tank empty, then fill when it's time to use the engine.
2) For the same reason, keep gas cans tightly sealed and don't store gas longer than you have to. This was always a good idea anyhow because when the fraction that evaporates easily is gone, it no longer burns correctly. Besides, gas vapor is poisonous and flammable.
3) If you have older equipment whose parts were not designed for ethanol, there are additives that will help.
4) Get all the fuel out of the system when storing engines off season. This was always a good idea, and is even more important with ethanol blend. Barry King; May 2011
All gas has ethanol now. Buy an ethanol fighting additive for small engines (found it at Lowe's so it is readily available) Empty old gas from your small engine for winter storage. Grace Nelson; June 2011