This guy has an excellent video on the topic:

https://www.youtube.com/watch?v=bEf9Fdvx_Sc

On that note, I have moved to non-ethanol fuel after replacing fuel lines and carbs on my small engines. I usually use Sta-Bil if it takes me a while to use the fuel. However, I always run my chainsaws and small engines dry when I know I won't be using them for a while.