Begin traveling towards the jump at your normal jumping speed. Hit the jump. Just before you hit the highest point in the air pull one of your feet off and kick it to the side. Don't kick it forward or backward as it throws the bike off and looks weird.

Your foot that is still on a pedal will drop straight down. Don't be surprised by this. It will throw your balance off when you first learn the trick. Hold your foot out to the side as long as you feel comfortable. Bring your foot back, put it on the pedal, and level your pedals out before you land.

When first attempting one-footers it will just be a really fast kick; out and back. When you have been doing 'em for a while you will be able to keep your foot out longer and longer.