I myself have settled on doing simple changes with fewer and fewer trot steps until the horse finally just gets the change. I've always found that balances them the best and makes the change smooth.
One trainer says "bounce" the horse off the wall. He wants you to head straight for the wall and then turn to knock them off balance so they'll change.
Another trainer says to gallop them across the diagonal as fast as you can pretending you are going to stay in the same direction and then make a sudden turn and throw all your body weight inside to, again, knock them off balance.
The one I hated the most used a pole. She always made people over use the crop and all that ended up was the horse would bolt for the change and half the time still not get it.
So, now that this is incredibly long, I was wondering how other people teach a horse to do a flying change and why? I've had great success with my way, but I want to know if I'm the only one who was told 8 million ways.