I realized quickly that going beyond the speed limit was too easy. (And potentially expensive - in many ways.)
Now I limit myself to reaching the speed limit and keeping the car there whenever possible, i.e. highest legal average speed. Figuring out alternative routes that are windier where people would normally say "you can only go 30 there" and try to keep the car in cruise control.
I soon realized that
not slowing and speeding back up was very kind to gas mileage. Conservation of momentum. Which incidentally are similar goals on a race track, no? Besides, it's always nice to catch up to a more powerful car in "the twisties". Puts the driving skills back in the driver's hands.
When we got 35 mpg in an unmodified 1993 3.3L Oldsmobile driving across the state I was hooked. Being a student strapped for cash also helped...