The important components of the game of billiards can be summarized into five different points:
1) Fundamentals (stance, stroke, bridge, grip)
2) Aiming
3) Cueball Control
4) Pattern Play
5) Mental Game
If you want to master the game of pool, you must master these five points.
Fundamentals are first and foremost. There are plenty of books and resources available to help you out. The best is to have a reputable instructor watch you play. Another idea is post a video to youtube or vimeo, and put a link in the forums at azbilliards.com. There are a lot of helpful people there that would be glad to critique your play.
Aiming is one of the most important parts of pool. If you can’t consistently pocket balls, the rest of the game is going to suffer. Many of the books available give the basics of ghostball aiming and other general techniques. Many people (including myself) have excelled their game in this area with a system such as CTE, the See-System or Perfect Aim. IMHO any aiming system that gives you an objective target (such as centers and edges) instead of invisible balls and invisible points is a huge benefit to aiming.
Cueball control is probably the one thing most pool players strive for their entire career. Position play is paramount in a solid game. To master position play, you must master the control of speed, english, throw/spin, and knowledge of cueball paths. One of the best ways to encompass these techniques is to practice racks of 9-ball and straight pool. These games require nearly every aspect of cueball control. Drills are another way to focus on a specific area. A gem I found recently is a short book by Ted G. Brown called the Wagon Wheel system. This system gives you an objective way to learn cueball control. You can get there in weeks instead of years. Check it out.
Pattern play is game-specific. 8-ball, 9-ball, straight pool, one-pocket, bank pool, all these games require their own pattern play techniques. Books are your friend, and practice running racks. keep track of your progress. For instance, run 10 racks of 9-ball, give yourself ball-in-hand after the break, shoot until you miss. Track how many balls you make. For 8-ball, try to break and run 10 racks, shoot until you miss. Give yourself a point for each pocketed ball of your denomination (solids or stripes), and 3 points for the 8-ball. Straight pool, keep track of your runs and always strive to top your best one. Reading about pattern play and running racks on the table are your best teachers.
The mental game is a must for masters of the game. Make sure you have a solid pre-shot routine. Keep a quiet and calm demeanor at the table. Don’t come unglued when things go wrong, keep your composure. Be a good winner and loser. If you do this, your game will accelerate and you put tremendous pressure on your opponent. There are plenty of resources on the subject, soak that knowledge in. Another gem I came across recently is Lee Brett’s The Secret Art of Pool. This a no-nonsense guide to the mental game, among many other game aspects such as the pre-shot routine. Short and to-the-point, the way it should be.