Gas tank cleaning?

Whats the best way to clean rust out of the inside of a gas tank? Is it worth it to mess with, or should I just go ahead and order a new one?

a motorcycle trick is to put water (i know sounds stupid) and rocks (also sounds stupid) and shake the piss out of it and it will knock all the crap off the walls. now remember the moto tank is >5 gallons so its a bit easier to handle... depending on how bad it really is i'd just get a new tank. no sense in fucking yourself later on down the line with a plugged fuel line or intermittent engine stall issues

Yeah thats what I was thinking, a new tank is on the way.