A great way to improve the sharpness and steadiness of your shots is to shadow practice them. This means practicing your shots without the ball. One of the best things that ever happened to me when I was a beginner was when I was told to shadow practice my forehand and backhand drives and loops, and side-to-side footwork, one hundred times a day. This was a primary reason why I went from beginner at age 16 to 1900+ in about two years.
For Beginning Players: focus on the basics. You want to develop smooth, repeatable shots and footwork. You might want to have a coach work with you first, so you aren't practicing bad habits. Once you know what to do, do perhaps fifty to a hundred forehand and backhand drives, and fifty to a hundred forehand and backhand loops. Then go side to side fifty to a hundred times, stroking each time (either all forehand, or alternate forehand and backhand).
One key thing: remember that strokes have three parts: backswing, forward swing, and back to ready position. Many players tend to just go back and forth (going directly from forward swing to backswing), which you never do in a game. The stroke should go through a triangular motion (dropping down to ready position), not just a back and forth motion.
For Intermediate Players: Focus on improving the speed, crispness and power of the shots and footwork. Think about the type of specific movements you do in a game, and mimic them. For example, if you want to develop a powerful forehand loop that you can use from all parts of the table, then shadow practice powerful forehand loops, from both the wide forehand and wide backhand, as well as from the middle, and practice moving from one spot to another. (Note--intermediate players should also use some of the techniques explained for advanced players.)
For Advanced Players: At this point, your shots are consistent and powerful. You should continue to do the shadow practice as explained for intermediate players. However, now you should add randomness. As you shadow practice, imagine you are playing a real match. Imagine a specific opponent, and play out the rallies--except now you are playing at whatever level you hope to attain. Want to be a world-class player? Then shadow practice rallies as if you are world-class! Instead of alternating forehand loops from side to side, add randomness - imagine your opponent spraying the ball all over the court. For example, after looping a forehand from the backhand court, your "opponent" might put one to the wide forehand, which you then cover; or he might block one right back to your backhand again, which you've vacated after the previous shot to get back into position, and so you either step around again for the forehand, or play a backhand attack shot.
You can also practice receive techniques - imagine an opponent's serve, read it, and return it. You might step in, drop a ball short or flip it, then step back and attack the next ball. Or you might shadow practice looping the deep serves. Think of what happens in a real match, and play out those points.
For All Players: You can practice everything this way, except for the actual timing of hitting the ball - and you can do that later at the table, with much faster, stronger and crisper shots because of the shadow practicing. And the nice thing is you can shadow practice anywhere - at work, at home, on the subway. (Okay, that last one might get you strange looks--but I've done it before!)