I may do it different than most people.
When I leave home to go camping (leaving Monday) I never fill up my tank.... I wait until I get to the campground and fill my tank up.
The day that we decide to leave and come home.. If I have any water left in the tank, I empty it at the campground.
Once or twice a season (from March to the end of October) I flush out my tank and use a little bleach.