Leg exercises are very important, especially if you are walking (which you should be since you are still young!!) Make sure you stretch your hamstrings, glutes and calves properly. These are the most used muscles when walking and this is where the power is stored on the backswing, so it's good to keep them limber. Remember, stretch slowly and DON'T bounce. Hold the stretch as long as you can - up to a minute if possible.