How to improve the fuel efficiency in my Ford Focus?

I've noticed that my Ford Focus isn't getting the best gas mileage. What steps can I take to improve its fuel efficiency and save money on gas?

One easy way to improve fuel efficiency is to make sure your tires are properly inflated. Under-inflated tires can decrease gas mileage by up to 0.3% for every 1 psi drop in pressure.

Another tip is to avoid unnecessary idling. If you're going to be stopped for more than 30 seconds, it's more fuel efficient to turn the engine off and restart it when you're ready to go again.