The inside hand is the turn signal; the outside hand is the steering wheel. After the inside hand has done its job, it should be STILL.
The base of the (horse's) neck needs to be stable. The bend should be through the body, not the neck.
The (horse's) nose needs to stay in line with the center of his chest at almost all times; otherwise he's overbent laterally.
Don't cross hands!
Spiraling in effectively requires turning the shoulders, lots of outside rein. Then you get "sit" and "lift."
To school turn on the haunches, leg yield and then straighten briefly first.
Don't accept little shuffle steps in trot-walk transitions; make them clean but forward. Fine line there!
In walk-canter transitions, don't get pulled forward; keep my position. For left lead, ask for slight haunches-in, since that's what he wants to do anyway, but it has to be MY idea and he can't throw his shoulder out. Anticipation is fine, but keep him forward.
Do canter-walk transitions in the same spot, using anticipation to assist with needed collection. Tracking right, a strong inside leg in the half-halt works well. Tracking left, MUST be straight; takes LOTS of outside rein (elbow to hip; use triceps) to keep shoulder from bulging out and tapping whip to keep inside hind under. Trying moving him off the right leg just as when tracking right. Get to walk as quickly as possible so he understands what is expected.