1. walk on your heels, toes pointed up. walk forwards then backwards for a total of some 50 yards, once a day is enough.
2. do backwards running -- at least half a mile and not necessarily all the distance at a time, e.g. on a track, do 2 laps forwards, then 1 lap backwards, etc. even better, do uphill sprints -- run up uphill, walk back to the bottom, repeat. important: push off the balls of your feet.