Just a few thoughts about "pacing". For those of you who don't know, pacing is when the dog's front and rear leg on the same side moves in the same direction rather than back and forth like a scissors. When a dog paces, it is usually because they are comfortable moving at that speed. Sometimes it is due to their structure. Some dogs are not built correctly and so the "normal" trotting gait for their breed is not comfortable for them, so instead they pace. Sometimes, it's a habit, again, usually due to comfort. Some dogs will pace as a way to preserve energy. Occasionally, there is a structrual problem that is causing pain and so the dog is compensating for it. Sometimes, and I see this often, dogs are trained to walk alongside their owners in "heel" position, or very close to the owners side. Many dogs are trained to do this and get in the habit of pacing to the point that if you then try to get them to trot they simply pace faster. Some breeds are more likely to pace and some breeds are actually permitted to pace when gaiting in the show ring.
I work with a lot of dogs who have gotten into the habit of pacing and have successfully helped them all learn to trot correctly. I have several exercises I use from cavaletti work to quick start strategies that help them to pop out quickly in a trot rather than lumber into a pace. Never, ever do I use leash corrections to modify this movement. It is not necessary, nor is it fair to punish a dog for moving comfortably. We are asking them to perform, to look showy and flashy, to allow strangers to handle and touch them, to be physically manipulated and to calmly cope with being surrounded by large groups of unfamiliar dogs weekend after weekend. It seems to me that we owe it to them to be understanding when they are simply trying to move their own bodies how they are comfortable doing so. Pacing is not "misbehavior" and should not be treated as such.