Setting up a Ghost Ball
You may find it helpful at first to imagine a ghost ball at impact. You can also speed up the learning process by placing a second cue ball in line with the object ball when you initially setup a new shot. Observe it's position carefully and then remove it prior to shooting. This will eliminate some of the guesswork and reduce your number of unsuccessful attempts.
Watching your Errors
Look for tendencies when you practice a specific shot. The example shows the two errors possible: undercutting and overcutting. An undercut shot comes from hitting the object ball too fully. Most beginners tend to undercut most of their shots. An overcut results from hitting the object ball too thinly.