1. Beat Level 1
2. press "menu" button
3. press space bar to go back into level 1 repeat steps 1-3 until level 7 is unlocked beat Level 7, or just beat level 1 again if you want to be safer (this is slower, though.) repeat steps 1-3 until level 10 is unlocked Beat Level 10

On level one, you'll want to let downhill sections give you more speed by going down hills riding on the back wheel, not letting the front wheel touch the ground. This will build up more momentum than simply biking down the hill normally.

For level 10, this mechanic actually comes into play more and makes it easier to get a good jump. Just bike down the long slope, try to ride down some of the mini-downhill parts on the back wheel, and that should make getting the jump at the end pretty easy.