I can tell you how I did it whether it right or not I can't say
Start out direct reining. Hold you hands about 8 inches apart and as you direct rein in the direction you want to go, at the same time lay the reins across the horses neck (opposite side that you want to go) over time and much repetition the horse should start getting the idea and you will only have to lay the reins on the neck for your cue.
I think it works better when your starting out to use a fairly thick rein. I like a rope type one
It takes time and patience as do all things horse training.