Welcome. The real answer is "it depends." If you are interested in State, county, or city campgrounds you probably will not only not get any discounts but your stay will be limited to two weeks or so. Corps of Engineers (COE) campgrounds honor the "geezer pass" I think. If you are over 60 you qualify for one. That is a card that gets you free or reduced entrance fees to many Federal sites.
If you are interested in private (commercial) campgrounds Good Sams, AAA, AARP, etc. can get you a reduced daily rate. Various membership programs have other discounts, some of them pretty steep. I'm talking about Coast to Coast (C2C), Thousand Trails (TT), Passport America (PA), etc. The catch is that you have to buy a membership. The trick is to buy a "used" membership, not a new one. A new one will set you back $1000 or more, while a used one can be had for 1/4 or that. Before you buy one, though, you really need to have some camping experience under your belt so you know your camping style. Some of those member parks may be a ways away from major area attractions.
For the best deals, plan on staying for a month or more. Many commercial campgrounds offer weekly or monthly rates. Typically the weekly rate is pay for six nights, stay for seven. The monthly rate is frequently about 2/3 the cost of four weeks.
Then there is the whole boondocking thing. That is staying somewhere, usually a lonely place with no facilities, using only what you have in your coach. A variation on that is "Wally-docking" which is staying the night (ONE night only) in a business parking lot. You MUST get permission first, since it isn't allowed everywhere, and the general practice is to buy something in the store. Beware, actually using a Wal-Mart can cost far more than a commercial campground (<grin>). Many Cracker Barrel stores have boondocking sites available. Even breakfast for two (or supper for two) there is still cheaper than a campground.
David Lininger, kb0zke
Heartland mpg 181 (sold)
1993 Foretravel U300 (for sale)