You'll need to precisely time your leaps in order to get far in the game, and the best way to do that is with practice. There are areas where you'll have to cross a wide gap, and it's easy to jump too soon. That will prevent you from clearing hte gap. When double jumping, you must also exercise caution. You'll get the most air if you jump again at the peak of the first leap. Otherwise, you're headed for another failure.