Originally Posted by Summer08
the gallop, or lope, (slower version) over a trot.
That is incorrect. A canter is the english version of the lope - which are 3-beat gaits and is what you are talking about cueing here.
A true gallop is a 4-beat gait. It looks similar to a fast canter but the left hind leg lands before the left front leg, creating the 4th beat. In a canter/lope the left hind and left front would land at the same time. (or vise-versa for the other lead)
I've never ridden a true gallop other than on a bolt and tend to avoid it because it is a more dangerous gait due to the speed involved. It can be cued for at first out of a canter by asking for more speed and moving your legs behind the girth when squeezing. Many horses won't go into a true gallop under saddle and will just stay in a canter because that is the way they are trained. Ex-race horses are good for it thought!