To cue for a walk: I gently squeeze with my both of my calves equally until my horse begins moving foward. When he does, I immediately release that pressure so that he is rewarded for his correct behavior. With some horses or some colts that are just learning, they may need bumping with your legs (instead of just squeezing) until you can refine your cue to a subtle squeeze.
To cue for a trot: It is the same cue as for the walk, but with MORE intensity. It is still perfectly equal between the two calves. I may also incorporate a cluck or kiss verbal sound to encourage them jumping to the trot.
To cue for a lope: Your horse must first know how to do simple lead changes while galloping. If they do not know their leads, you aren't going to get them to move into the correct lope from a walk. To cue my horse from a walk for the left lead, I move my right leg back slightly to bump him with my heel. Therefore, he knows the difference between a soft squeeze with both legs (walk), and a hard squeeze with both legs (trot), and a bump with my heel for the corresponding gallop.
To get a horse to be responsive to subtle cues like this, you have to always be 100% consistent all the time. That means, you always specify what you want so they learn to always be paying attention. And you have to do it the exact same way every time.
∞•*˚ Βгįťţαňγ ˚*•∞
It is not enough to know how to ride; one must know how to fall.