For me, it's really about the SEAT. If I can get a good half halt with my seat, and not my hands, keeping my leg on, then my horses rebalance themselves without tensing up in their back and changing their tempo. My "test" is, can I get a canter I like, then generously loop the reins AT THE SAME MOMENT that I am half-halting with my seat, and have it work out? If I do, I'm good to go. If the horse either falls forward on his face, or breaks into a trot, or quickens his tempo, then the half-halt from the seat needs to get better. I'm looking for a horse that says balanced and soft while I give the reins, so I can keep my leg there (if not necessarily asking) in the half halt.