This is an older thread but its nice to see it bumped because the first post is really full of quality tips. I especially appreciate the info re: tire pressure.
I would add that I have found
MSN Autos' Gas Price page to be more reliable and cover more stations (in my area at least) than the aforementioned Gas Buddy site.
Also, I formerly thought that lower priced gas was fine and although I didn't use Hess (for one) very often, I did buy my gas at Murphy USA (Wal-Mart, Sam's.) This was often the best price in town, especially when using a Wal-Mart shopping card (gift card) to pay for it (additional 3 cents per gallon discount.) However, after doing this for a couple of months, my car began to knock severely. It was so bad that I thought I was about to throw a rod or something. A mechanic suggested that I switch gasoline. When I did, the knocking stopped and has never returned. Now, I look for the lowest cost gasoline excluding Hess, Murphy USA, and the like. Fortunately, the BP near my house is often among the cheapest in my area.
(Just to be fair, I should also point out that during the same time-frame as my vehicle was knocking, my wife's car, which was also filled at the same Murphy station, never showed any signs of problems. However, the fact that my car did is, to me, a tell-tale sign of the fact that it is lower quality. Not only this, but since that time a friend of mine has concluded that his vehicles get less gas mileage when using Murphy USA than when using Exxon/Shell, etc.; indicating further that the cheapest isn't always the best deal.)