Visualize what your horse's legs do when he is on the left lead, for example. The left front and left hind legs extend farther forward than the right. It follows, then, that the left shoulder and hip also move farther forward than the right. Thus, there is a different feel to the left side's energy than the right. Now focus on what your body does in response to the horse's movement. You will probably feel that your left leg and body are reacting to what your horse's left side is doing. When you think that you are tuning into the left lead, stop, reverse direction and do the same thing on the right lead. Once you have mastered what the leads feel like, ask your horse to lope and then tell your friend what lead you have taken. When you are consistently correct, go to a larger arena and continue practicing. It will take time and concentration, but you will get it.