I'm teaching a beginner friend position play. I've noticed one big difference between me and him.
I can aim the cue ball *very* accurately to hit an *exact* spot on the object ball even 1/8 inch difference this way or that way.
My friend can't do this. If he is hitting an object ball which is "hanging" in the pocket, the cue ball can hit the object ball anywhere within a 1 inch area. So each time he sets up the same shot - the cue ball in the same starting place, object ball hanging in the pocket, the cue ball will come back off the shot in a different direction. Maybe to the left, maybe to the right, maybe follow the object ball into the pocket. No telling where the cue ball will go after the shot!
I can hit the object ball in a specific spot, and by doing this, I know that the cue ball will come off the shot in a certain direction. So I can always hit the same shot and always get the cue ball to come off the shot to the left. Or to the right.
I'm learning that being this accurate is a big help to leaving position with many of my shots.
So I can have what appears to be a straight in shot. Well I can "cheat the pocket". I can shoot the object ball to the left side of the pocket or to the right side of the pocket. And this will change where the cue ball goes after the shot.
The way I got to be so accurate is I have quadruple shimmed pockets on my table at home. The corner pockets are 3 3/4" and the side pockets are 3 7/8". Then just playing on this table for several years. It was impossible for me to play on this table at first! I had to learn how to aim accurately, not just send the object ball in the direction of the pocket and let it wobble in.
So being able to hit the object ball in an exact spot is a big help.
Then get Dr. Dave's DVD at the following link. This will teach you the 30 and 90 degree rules as well and other basic stuff. With every shot you have many options as to where you can get the cue ball to go after the shot. Dr. Dave teaches you what your options are. Don't get the DVD and watch it like a movie. Watch a shot, then hit pause and go practice that shot. Then watch next shot/practice. This stuff is worth its weight in gold! Get his DVD here...
http://www.engr.colostate.edu/~dga/pool/cd_dvd/dvd_description.html
For speed control, break a rack of balls and shoot each ball so it rolls up to the pocket and stops just before dropping into the pocket. With this practice, you learn that with a full on hit, the object ball will take all of the speed of the cue ball and the cue ball will "die". With a thin cut shot, the object ball will take very little speed from the cue ball and the cue ball will go flying off into space. So need more speed on thin cuts to get object ball to pocket and very little speed with a full on hit. AND cue ball tends to die with full on hit, cue ball retains most of its speed with a thin cut. Knowing exactly how hard to hit the shot to pocket the ball (depending on full hit, 3/4 hit, 1/2 hit, etc.) can come in very handy sometimes.
Also practice shooting just the cue ball 1/2 diamond distance, 1 diamond, 2 diamonds, 3, 4, etc. Shoot to far rail and stop. To far rail and back 1 diamond, then back 2, 3, etc. All the way up to 3 rails.
After practicing this stuff for about a year, you will see a shot, know how hard you need to shoot to pocket the ball, will know the general direction the cue ball will go after the shot with follow or stun, and will be able to use follow, stop (stun), or draw to get the cue ball to go where you want after the shot. Then you can slowly learn how much speed to apply to make the shot and get the cue ball to roll as far as you want. (I think this part can take a lifetime!)