1) Check your air filter. A clean air filter can improve gas efficiency by up to 10%!
2) Align your tires. Tires that aren't properly aligned can result in your engine having to work harder than it would otherwise.
3) Take it slow. For every 5 miles per hour you reduce your speed, you can reduce your fuel consumption by 7%.
4) Keep it smooth. Jerky starts and stops can quickly add to your gas bill. Poor drivers can add an addition 1/3 on to their gas bill.
5) Take a break from the brake. Keeping your foot on the brakes can wear out your brake pads and increase your gas consumption by 35%
Small changes here and there may seem insignificant now, but when you find yourself stopping to fill up less frequently, you find out just how much they can add up.