Join Passport America for cheaper campground rates. We use this a lot when traveling and save the membership fee in just a couple of nights.
Browse the marked down bakery, meat, produce sections at the market with immediate use in mind. At places like Walmart with the hot chickens, look in the cooler around that area as many times at closing, all chickens not purchased are refrigerated and then offered for sale at a lower price.
We use Gas Buddy to find the cheapest gas prices. We have found that even though we are 36' pulling a trailer we can get into many/most regular stations to take advantage of the lower prices.
If you use a laundromat, don't go until you have full loads AND most campgrounds have laundry centers that are cheaper, take advantage of that when you find it.