Well, to give you a more detailed answer, I changed my way of driving a little when the petrol prices started to rise and rise, and have now got used to changing my gears earlier, using the fifth in town, too, accelerting over longer periods of time, not overtaking "only because I can", trying to look far ahead to be able to reduce speed early simply by taking the foot off the accelerator etc.
I didn't believe it would be that effective, but true fact is that today I'm thus saving up to 12 % of petrol compared to my earlier driving (and the changes in my behaviour are totally minor).
Another thing: make sure you always have enough air in your tyres. That, too, helps a lot.
And I plan my journeys better, combine shopping with taking Sabine to the pool and such, to avoid unnecessary trips.