Think before you shoot and don't waste tape. Be aware of what you're shooting and when the tape is rolling. Don't roll tape unless you're taking a shot.
For example, don't roll tape when you're changing from one shot to another or focusing. Wait until you have the shot you want to roll tape.
That way you'll save a huge amount of time later when you're capturing your video into a computer and you won't have to go through a hour-long tape with a lot of junk to find the 20 minutes of shots you want.
And you'll save money by using less tape.