As I travel I find many towns where gas price varies as much as 62 cents per gallon (highest I've experienced-seen this week) between stations. It always wonder if people see the signs when I see someone filling up at a station that is across the street from another station which is 30 cents cheaper. Both are major brands too.
As I travel over 25,000 miles per year, some tips that I have found:
1) Use gas buddy and the online gas price resources
2) Use membership stations, such as Sam's club, Costco etc.
3) Use truck stops, and get their RV discount card if they have one. Pilot for example will give you an RV card good for 2 cents off per gallon at Pilot and Flying J.
4) Ask clerks who has the best gas prices in town.
5) Use your GPS device to look up upcoming stations. Some brands tend to have better pricing than others. I have found where several stations are together prices are usually (but not always) better than where there is only one station.
6) When prices are going up fill up. When prices are going down don't fill up if you don't plan to travel a lot.
7) Stations a block or two into a city (used by locals) are often 20-30 cents cheaper than ones on the freeway. I don't mean drive all over town, just look down the street.
8) Keep an eye on prices as you drive, and don't get into a situation where you are almost empty and forced to buy. I've planned to gas up in a town, and found all 3 stations with high prices, so driven on to the next town, and saved 30 cents a gallon. Of course there are towns where every station is the same price and you know the fuel distributors must have coffee together!
9) Remember lessons from previous trips. An example: for years at the main Needles off-ramp (after driving through the desert with no stations for a couple hours) stations have been about 50 cents a gallon higher than ones a few blocks away.
Perhaps this sounds cheap, but it sure adds up when on a limited budget. Every time I save a few dollars in gas I say, there is $ that can use towards a special lunch etc.