The best way to save on fuel is to use less of it.
Having an overall plan in mind can save backtracking and inefficient routes. Snowbirds tend to move in circuits in order to follow good weather.
Maximizing stays at one camp lessens the amount of overall traveling one does. This might mean staying at a particular area for the whole 14 days1) then moving to the next spot. An extreme example would be staying at a Long Term Visitors Area.
When traveling across multiple states or when camping near a state border, keep these general trends2) in mind:
Arizona < California
Louisiana < Texas < New Mexico
Ohio < Michigan
West Virginia < Pennsylvania
Massachusetts < Connecticut
Alabama3) < Georgia