At first you can slowly tap, but as the bar at the top of your screen drops faster as you make progress, you will eventually need to tap faster. Slowly build up your tapping speed as you get used to controlling your character. Accidentally tapping the wrong side will end the game. As you reach the fast paced part of the game, look for long straight-aways where you do not need to switch sides. This allows you to concentrate on tapping as fast as possible. The straight-aways are the best way to regain stamina for the energy bar.