I'm just skimming all the comments quickly but would add that sometimes things are taught backwards. I think its called back chaining. (Not necessarily the stop though)
We started getting a sit at a distance by throwing a sticky treat over the head. It is tricky but to begin with it doesn't matter. I think the book said do it with a wall or skirting board behind the dog so the treat doesn't go too far.
The dog automatically looks up and sits. Start close then get some distance. You then go on to use the hand signal and whistle. Hope that helps.
Teaching a left or right move I think we did by -as the dog comes towards you throw a treat with which ever arm/direction you want them to go, eventually adding a cue. You can use a clicker for all this too.
Folks who do agility must teach their dogs somehow!
I tried to teach mine a lot of this years ago but life just got in the way.