A more fuel-efficient Ford Focus

Do you know of any other ways on how to make my 2010 Ford Focus hatchback more fuel efficient? I know that its fuel efficiency is not that great but I didn't categorize it as a model with very poor fuel efficiency prior to purchasing it. When I bought this car back in 2010, me and my wife were just newly wed and spending bucks on fuel wasn't really much of a biggie. But when my son was born early this year, I realized what fuel efficiency really means! Haha! Now looking at the rise and fall of gas prices and the like which I didn't mind a couple of years ago! I don't wanna sell this car as I love it. I just wanna know what else to do to make it more fuel efficient. Any tips are appreciated! Thanks to all!