Practicing by yourself on the court is very important. It is the most effective way to gain muscle memory. Practice generates good habits and breaks bad habits. Your body learns what to do, so that in a game situation your brain can be concerned with things like strategy rather than mechanics. You should practice at least as much as you play.
 

Making practice interesting

Some people like to practice, others hate it. You will almost certainly get bored if you don't have a structured practice session. Just hitting the ball around gets old in a hurry. You can make practice more interesting simply by counting. Each of the following drills has a goal. I compete against myself by noting if I am getting better at each drill. There is no need to spend more than one hour at a time practicing, unless you enjoy it. As you get better, you will find that that you will have time to add more drills or make the current drills more difficult by deducting points for skipping, leaving shots up, etc. Be sure to make time during the session to practice your serves. The serve is the only opportunity during a game where you are in the front court, your opponent is way back in deep court, you get to choose the shot and where you hit it from, and you get to drop and hit the ball. Practicing your serves allows you to make the most of this opportunity.
 

These drills are designed for collegiate racquetball team players. Less experienced players might find them difficult. If they are difficult for you, just modify them. For example, drop and hit rather than toss and hit. Don't worry if a cross court pass comes off the back wall, as long as it actually goes across court. Hit 10 instead of 25 or 50, etc.

I have tried many different drills over the years. These are the ones that have helped my game the most. These drills assume that you are right handed. If you are a lefty, make the obvious adjustments.

Practice improves your game. Playing allows you to see how much your game has improved. Play less, practice more, play better.
 

Warm-up

Lunges/phantom strokes (no ball). Start in the ready position as if prepared to return serve. Take a step to the forehand side, execute a forehand stroke. Return to ready position. Take a step to the backhand side, execute a backhand stroke. Return to ready position. Repeat 50 times. Concentrate on form.
 

Ceiling Ball Drill

Hit a good ceiling ball. A good ceiling ball is a difficult offensive opportunity because it winds up close to the back wall. The natural response is to return another ceiling ball. Repeat 50 times. To make this drill more difficult, don't count balls that come up short or come off the back wall. Note how important the angle of your racquet face is. Try to get the strings pointed toward the ceiling about four feet in front of the front wall.
 

As a variation on this drill, if the ceiling ball is long and comes off the back wall, execute a passing shot. If it is short, execute a passing shot. Don't try to kill the ball from deep court. Repeat until you have hit 50 good ceiling balls (neither short nor long).
 

Toss and Hit Drill
 

Stand in the middle of the court on the dotted line facing forward in the ready position. Hold the ball in your left hand. Toss the ball gently diagonally toward the right hand side wall. Toss the ball so that it takes a nice bounce, but not so hard that it bounces off the side wall or bounces away from you so you have to chase it. Take a cross-over step and execute a down the line shot. Repeat until you have hit 5 good DTL shots. (A good DTL travels the length of court close to the side wall without touching the side wall and bounces twice before hitting the back wall.) You should be hitting close to the short line. Repeat the exercise hitting 5 good pinch shots. (A good pinch shot hits the side wall, then the front wall, bouncing twice before it hits the other side wall.) Repeat again hitting 5 good cross-court or wide-angle passes. Repeat on the backhand side.

Move back five feet and repeat the exercise, now hitting all 15 of your shots near the dotted line.

Move to within two feet or so of the back wall and repeat the exercise. You should be contacting the ball about four feet in front of the back wall. Don't hit any pinch shots because you are too far away from the front wall. Instead hit 10 DTL's and 10 cross-court or wide angle shots.

I like this drill because it forces you to take the cross over step before hitting. This is important for correct footwork. A very common mistake is for players to hit "wrong footed." Interestingly, I see more players hitting the forehand off the wrong foot than hitting the backhand wrong footed (perhaps because they can more easily "muscle" the forehand).

Finally, set up within a foot of the back wall, facing the side wall. Bounce the ball into the back wall and, on the rebound, hit a DTL. Repeat until you have hit 10 DTL and 10 CC or WA shots. Be sure to shuffle out from the wall as you let the ball drop into your hitting zone. This is good practice for hitting balls off the back wall.

To make this exercise more challenging, hit 5 CC and 5 WA shots and don't count the shot if you meant to hit a CC and you accidentally hit a WA or vice versa.

If you find this drill difficult, do the basic drop and hit drill instead. Everything is the same except that you set up about 5 feet from the side wall, facing the side wall, drop the ball out and away from yourself, and execute the same shots. Try not to drop the ball too close to your body and jam yourself. You should be able to extend your arm on the shot. If you have trouble timing the drop and hit, just let the ball bounce twice before hitting it. (Letting the ball bounce twice is also a good drill for short-hopping the ball.)
 
 

Splat and DTL Drill

Stand on the dotted line, about three feet from the side wall, facing the side wall. Drop the ball so that it bounces within 6 inches of the side wall. Don't bounce the ball so that it rebounds off the side wall. Hit a good splat shot. (Hit the ball using the strings near the top of the racquet since the ball is so close to the side wall.) The ball is hit into the side wall within a foot or so of where you contact it, rebounds to the front wall, and bounces twice before hitting the other side wall. If you do it right, you should here the distinct "splat" sound. Now move two feet closer to the front wall and repeat. Keep moving at two-foot increments until you are two feet in front of the foot fault line. Now bounce the ball gently into the front wall and, on the rebound, execute a splat or pinch, depending on how far away the ball is from the front wall.

Now bounce the ball into the front wall and, on the rebound, hit a DTL shot. Move back to the foot fault line. Drop the ball within a foot or so of the side wall and execute a DTL. Keep using the top of the racquet because the ball is close to the side wall. Move back in two-foot increments, repeating the DTL shots until you are behind the dotted line. This allows you to practice both the splat and the DTL from a position close to the side wall. The DTL is the better shot if your opponent is in good center court position, and is a higher percentage shot anyway. Repeat the whole exercise on the backhand side.

This drill can be made more difficult by standing in center court, tossing the ball diagonally toward the side wall, taking the cross-over step and hitting the splat, assuming the ball is within 6 inches of the side wall. If it is not very close to the side wall, hit a pinch instead.
 

Reverse Pinch Drill

 Stand on the dotted line on the left hand side wall, facing the opposite side wall. Drop and hit a forehand reverse pinch (which hits the left side wall, front wall, and bounces twice before hitting the right hand side wall). Take two steps toward the other side wall and repeat. You should hit five good reverse pinches from the extreme left to the extreme right side of the dotted line. Turn around and repeat with backhand reverse pinches. Move to the short line and repeat the whole exercise. Don't practice reverse pinches from behind the dotted line. It is a low percentage shot from the back court.

To make this drill more challenging, deduct a point for any shot that skips or is left up on the opposite side wall.
 

Scramble Drill

 Stand in good center court position about two feet behind the dotted line. Drop and hit a pinch shot, now without touching the ball with your hand, hit 50 good offensive shots (DTL, CC, WA, pinch, reverse pinch). You will have to move to get to the ball. If the ball bounces twice, ok. Just hit it, baby. If it rolls dead, use your racquet to get it bouncing again. You are not allowed to drop and hit. If you skip the ball, deduct one point. Don't stop until you have hit 50 good shots. If you want to make it slightly more difficult, hit 25 forehands and 25 backhands, or count only the backhands.
 

Set Up Drill

 Hit a short ceiling ball on the forehand side. Hit a good DTL. Repeat until you have hit 5 good DTL shots. Repeat, hitting 5 CC or WA shots. Repeat on the backhand side.

Hit a ball long off the back wall. On the forehand side, execute 5 DTL, 5 pinches, and 5 CC or WA shots. Repeat on backhand.

Stand on the left hand side wall at the dotted line. Hit a left up forehand reverse pinch into the left hand wall that rebounds off the right hand side wall into mid court. Execute 5 forehand DTL and 5 CC or WA shots. (Don't re-pinch a pinch.) Now stand on the right hand side wall at the dotted line and hit a left-up backhand reverse pinch that rebounds into mid court. Execute backhand 5 DTL and 5 CC or WA shots.
 

Overhead Drill

Hit a backhand ceiling ball cross court to the forehand side. Hit a good overhead cross court pass. Repeat 5 times.

As a variant of this drill, if your ceiling ball is short, or rebounds off the back wall, hit a standard passing shot. The overhead is only for ceiling balls that would normally be returned to the ceiling.
 

Drive Serve Drill

Set up in the right hand serve position and hit 5 good drive serves to the forehand. Be sure that the ball strikes the floor behind the short line and bounces twice before reaching the back wall. Since you are on the right hand side, the serve is a screen and doesn't count if it hits the back wall more than a foot from the right hand side wall. Try to make it hit the side wall or go directly into the corner. To make it more interesting, consider deducting a point if the serve bounces only once before hitting the back wall, allowing an offensive return.

Repeat the exercise hitting 5 good drive serves to the backhand from the same position. Consider it a screen serve if it hits the back wall more that three feet from the side wall.

Move to the center serving position. Repeat. Serves must hit the back wall within two feet of the side wall to avoid being called screens.

Move to the left hand serving position. Repeat. Serves must be within one foot of the left hand wall or three feet of the right hand side wall to avoid being screens.
 

Z-Serve Drill

Set up as in the drive serve drill and hit drive Z serves from the left and right serving positions. I don't recommend hitting Z's from the center position, because the angle is bad.
 

Jam Serve Drill

Set up in the same three positions and hit jam serves to the receiver's backhand and forehand. The ball should hit the front wall about four feet high and about eight feet from the side wall. It then travels to the side wall and contacts it about three feet high and approximately at the dotted line. It should take its first bounce about 2-3 feet in front of the back wall in the center of the court.
 

Lob Serve Drill

Stand in the left hand serving position so that the racquet contacts the ball on the midline of the court. Hit lobs, half-lobs, and nick lobs to the forehand and backhand. This is a good cool down exercise. It is also a good warm up exercise instead of, or in addition to, hitting ceiling balls.