Sprint Intervals!
Make sure you warm up effectively before jumping into this one. Run about 3 min, followed by 30 sec each of:
High Knees
Butt Kicks
Side Shuffle (Right and Left)
Carioca (Right and Left)
Skips
Then 10 meter sprints. Perform 10 runs, increasing pace with each one until you finish at a full sprint.
Workout:
Find a hill for this one. Mark off a distance of about 40 yards. Sprint hard up the hill and walk back down. Repeat for 12-15 rounds of until you can't maintain your pace running up the hill.