OK, here's how the game works.
First, you get the angle by clicking it and hold it. While holding it you can select the power level of the hit. The bishie will fly after getting hit by a bike.
Depending on who you hit standing around you'll get different reactions. If you hit a guy you'll either slow down or change angle (specific guys, you'll know soon). If you hit a girl, depending on which one they are, they often give you boost to your speed (so the bishie can go further) or stop you. Yes, the girl with glasses is the stop girl.
Remember, there are combos abound, so when it says Special and click, click. You'll know when you click with specials box on your right. Combos happen when the bishie hits two or more girls at once without touching the ground.
Etc etc, you'll find out sooner or later
And for the record, my highest right now is 5009.78m.