If you have too much weight on your back foot at impact -- two signs that you do are slicing and hitting behind the ball -- practice swinging on a downslope.
Gravity will pull you down the hill as you swing through, so you'll naturally shift to your front foot.
Swinging downhill should also improve your swing path. Players who hang back tend to cut across the ball because their arms pull inward or flip the club to the left. With your weight moving toward the target, your arms are free to extend down the line (right).
So find a downslope -- the front of the practice tee or when you walk off a tee box -- and groove that forward shift. You'll start hitting all your shots more solidly.
*Ranked No. 1 on Golf Digest's 50 Greatest Teachers, Harmon runs the Butch Harmon School of Golf, at Rio Secco, Henderson, Nev. *