I think there have not been any replies so far because many people don't know how to practice properly. this is VITAL to learning anything and performing well. Competition is nice but practice time alone on the table is absolutely crucial to this game (or any other) and should be the majority of your time at least in the beginning.
I have an incredibly boring practice routine that I have done for quite some time now. The upside is it has produced great results! basically I practice 3 groups of shots constantly.
Most important for me is
1) Short Angles!! the other two are
2) long 3-rail naturals and
3) outside the ball 3 long three rail shots.
If you practice these three you should notice great improvement but it takes time.
the short angles I practice with all 3 within 1 diamond up the long rail, 2 diamonds up, 3 diamonds up, then 1 ball with 1 diamond up (or less) and the other moved b/w 2 and 3 diamonds and so forth. practice shooting off both balls and with moving your cueball closer to and further from the 2nd ball as well as up and down the table.
the long 3 natural can be a bit more tricky when you start studying the kisses, but for now, practice with the 3rd ball in the corner (make it an easy target for yourself at first) then with the 2nd ball about half way up the table, 1 diamond away from the long rail and your cue ball about a foot or so behind it in line with the short rails. then create some distance between the two by moving the cue ball back and/or the 2nd ball forward. then move cue ball more left or more right and see how things change for you. (only minor movements are necessary)
outside the ball - try placing the 3rd ball about 1 diamond up the long rail, close and close to it, 2nd ball about 1 diamond away from both rails, cue ball around a diamond out from the long rail, half way up. then move the balls around a bit.
the key is repetition...
see attachment. sorry if the diag is a little shakey - blasted one out with Paint.. angles and dimensions i'm sure are not exactly correct but you'll get the idea