I walk to work, ride my bike, or take the bus if the weather is bad. I realize this isn't an option for everyone, but for those who are able to do so, it can make a very big difference.
We'll combine errands, be less likely to take vacations where there's a lot of driving. Our cars are 12 and 13 years old so when we replace them, we'll obviously look for something with good gas mileage. (Hopefully our Prizm will live quite a while longer, as they've stopped making them. That's what I'd want again!) We've also considered getting a motorcycle for my husband to ride to work when the weather is good. That would definitely save on mileage.
We're living well below our means right now so it won't be a hardship, but I'll miss being able to tour the wineries in our state as frequently as we do now!