Send somebody back to the minors
Literally this means a baseball player is not good enough to play in the major league (professional baseball), and should go back and play on a smaller, minor league team for a while to bring his skills up to the necessary level. The phrase is used outside of baseball to refer to someone who is in need of more training or preparation.
Exact aim, right on target.
Depends upon the context. In the Old West, if two gunslingers were going to have a shootout or a dual, they would face each other and one would say "draw" instead of "1-2-3 go" or "ready, aim, shoot" when it was time to pull their guns out of their holsters and commence firing.
Student or Learner