What do you do to keep a gasonline fuel system clean?

What is the best way to store something you use once a year like a combine?  Drain it or additive?

Once it is gunked up, how do you clean it?

Is there anything that will take those really caked deposits off a sediment bowl or do you just wipe it clean and not worry about it?

If I had some E-85 I think I would dry that to clean it.

Thanks,

Ed