Imagine the line you want to hit with the disc. Trace it from the basket, to the apex of the shot, back to the pad, and all the way back to the farthest point of your reach back. Reach back and touch the spot with the disc and adjust your arm and get it on the same line that you just created in your head. That will tell you where you need to go with your run up and swing motion.
As far as what disc to use and whatnot. Practice hitting the apex that someone pointed out earlier, throwing with nose up, nose down, flat, hyzer+ nose down, anny + nose up etc etc, use every disc in your bag. If you do this enough times, you'll learn more than one shot. I say to practice throwing at the apex, on your imaginary line, because that is the point where the disc is supposed to take over the workload and get the job done. Your job is to get it to that point with the right disc, at the right speed, with the right angles.
But, that's just like my opinion, man.