How do I increase the gas mileage on my Ford Focus?

I recently purchased a Ford Focus and have noticed that the gas mileage is not as good as I expected. What are some tips or modifications I can make to improve its gas mileage?

One easy way to improve gas mileage is to check your tire pressure regularly. Underinflated tires can decrease fuel efficiency.

Another tip is to avoid idling for long periods of time. Turn off your engine if you are going to be stopped for more than a minute.