To get the most out of your practice session, you should repeat the same motions over and over until they become automatic. Think of one recent shot you missed pocketing or positioning the cue ball, and set that shot up how you remember it.
For the next hour, shoot only that shot. Analyze every aspect of the shot, especially your line of aim, tip contact, and stroke speed. Visualize the shot before you start your routine and don't get lazy!
Concentrate on every attempt, even more than you would during competition. For every mistake you make, try to figure out the cause of the mistake. If you aren't making mistakes, then move on to a more difficult shot!
If you don't have an hour to practice, then even 15 minutes of solid practice can be more beneficial than hours of shooting random shots.