Passport America membership has saved us a bunch of $$ over the years. It is a 50% off reg. price at campgrounds in their list. You usually break even with the fee after a couple of nights. Only downside is that some campgrounds have blackout days like not valid on holidays or Fri. and Sat. nights.
Other times when available we stay in Nat. Parks, COE, Nat. Forest, Walmart, Sams, Cracker Barrel, city and county parks and boondock. Oh yeah, in friends yards when asked.