Here's a collection of some things that came up at the clinic:
When starting to do flying lead changes under saddle, don't force the timing. Set the horse up and then allow the horse to figure out how to organize its feet without pressure. The timing will be able to be refined once the horse has been allowed to develop the skill without pressure. Many horses are driven into flying lead changes and as a result are very worried about them. It should be as easy as when the horse does it in the pasture - your job is to set it up and then stay out of the way.
Too much lateral flexion work leads to horses where the head is disconnected from the body - these horses have trouble traveling straight and also doing turns without loosing the bend.
If your horse knows a certain set of cues for an action, and you want to train the horse to do the action using a new set of cues, don't throw away the existing learning but instead introduce the new cue you want and use the old learning as needed for a secondary cue. As time goes on the old way of cuing can drop away and the new one will be the one the horse knows.
If the horses falls behind the vertical or dives with its head, just gently lift one rein to slightly tip the horse's head.
If the horse's front leg is about the same length as your leg - true for most horses we can easily mount from the ground - then the horse's motion will be easy for you to follow with your body. A taller rider can easily adjust to a smaller horse, but a smaller rider on a larger horse will have to make more adjustments to follow the larger horse's larger movements without blocking the motion.
Don't start a fight where there isn't one - ignore stuff that isn't important to what you are doing and it will likely fade away. If you fight about it, it becomes important. This is part of focussing on what you do want, instead of what you don't want.
If you make a mistake, you can feel bad about it if you want but feeling bad doesn't help you or your horse.
Don't expect the horse to have 100% of its attention on you. Do you ever have 100% of your attention on your horse? If the horse can do its job, and you are at least as important to the horse as a distraction, that's enough.
Stay out of the horse's way and make it easy for the horse can be free to move and do what you're asking.