Crackdown Hints

This sometimes works, and only in certain conditions. Pick up any random flat item -- although dead bodies sometimes work -- jump into the air with the object in hand.

At the azimuth of the jump, toss the object downwards and sometimes your character will stop as if he stood on the ground (but in the middle of the air); if you jump again, your guy will start a jump from that spot in the air. It might prove helpful for some higher areas when your jump isn't high enough yet (due to lack of agility orbs or leveling).