It is easy - just buy gas the day before it goes up 20 cents. The best time to fill up your tank is below the 50dma. Yesterday I filled up the tank of my Mercedes-Benz SLR McLaren coupe (aka '92 Toyota Corolla) for $1.95/gallon and today it is going for $2.17.
Next time I might buy a couple hundred gallons extra and set up a "gas stand" in the front yard.