You've heard the story of the musician walking along a street in New York with an instrument case under his arm. A car pulls along side and the occupant asks, "Young man, how do I get to Carnegie Hall?" The musician replies: "Practice, man! Practice!"
That advice also applies to tennis. You cannot improve your game by just playing. Competing only demonstrates your ability to play the game. Practice works to improve your strokes.
How many of us just want to go out and play and play and play and never really have a practice session. (We're all somewhat guilty.)
Playing does not provide enough repetitions of any stroke nor the opportunity for you to analyze and improve it. The only way to accomplish that is to practice.
Find a hitting partner willing to practice with you and let you drill on certain strokes. Reciprocate, of course. If you can't find a hitting partner willing to practice, find a backboard or a wall. They're great competitors. Better still, try a ball machine. You have to feed them once in awhile, but they never tire of feeding you the ball you want to hit. Students of American Sign Language know you must see a sign 300 times before you really learn it. The same could be said for any tennis stroke.
Practice is more than just hitting balls over and over with your hitting partner. That's just warming up... or warming over weaknesses, if they are exercised at all. When you do, practice with specific goals. Try to develop proper stroke progressions the way you were taught and if you weren't taught, find someone who can teach you, preferably a certified instructor. You're never too far along to take advantage of proper instruction.
That is not to say a good hitting partner can't often relate some valuable observations of your game. But be wary. As most skiers know, everyone is a born ski instructor. It seems to be innate. The same is true in tennis. Remember, free advice is usually worth the price.
There is only one kind of practice and that's "Good Practice," practice with a purpose, practice with a capital "P". That may sound a bit demagogic. "What, pray tell, do you mean by 'Good Practice?'"
It's a fair question: what is a "Good Practice?" There are many parts to a good practice. A good practice session starts with an objective and includes numerous repetitions. Have a plan. What do you want to accomplish? If there is a particular stroke you want to work on, be sure you know the proper progressions through that stroke. Work on things you are not good at. "I can't do that!" is not a proper response. The answer to why you can't is in the proper mechanics of the stroke. Find them out. Try them. Make errors to the point of frustration, then make some more. It will come. (Note well: an error is when you know what to do and don't succeed in doing it right. A mistake is when you just don't know what is correct.)
You may notice at the club level many strokes that are "unorthodox," to say the least, but the perpetrators use them consistently and with some success. What's wrong with that? Nothing, except that the stroke has nowhere to go. It will never get better, because it has no foundation in proper mechanics.
One way to start a good practice is to warm up with a close range volley. Get the ball over the net twenty times without a miss. Move back to the service line and do it again. Retreat to the baseline and hit ground strokes over the net twenty times, at least. Are you stroking the ball, accelerating through the hitting zone, or just flailing away as hard as you can? Can you hit to zones on demand? Better still, are you giving your hitting partner a ball he or she can deal with? Are you in control?
Next move into an area where you want to improve, usually one that's giving you difficulty. It's probably the one you like least. Start slowly. Work on mechanics. Hone them until your confidence in the stroke becomes apparent. If things don't go too well, it's still a plus. Gains were made. You'll see.
Tennis magazine published an article (August 1997) which describes "15 Perfect Practice Drills," each one authored by a prominent teaching pro well known in the game. It's a good idea to save articles like this in plastic sheet protectors and refer to them often. The instruction includes a serving drill, drills on ground-stroke accuracy, depth, consistency and angles. Overhead, volley, soft hands, return of service drills are among the others, all worthwhile.
You can't beat a backboard for a productive practice session. If you don't have a hitting partner or an instructor, find a wall, but plan your session. A backboard can wear you out. It doesn't have to be that dreary ba-bump, ba-bump, ba-bump! There are literally dozens and dozens of backboard drills available for one or more persons. They are challenging and they are fun. For example, USTA has a video called "Backboard Tennis." There is also a supplement to the USPTR Instructor's Manual produced by Mike Bachicha and Dennis Van der Meer entitled "Backboard Drills for Individuals and Groups." It alone has over fifty drills and games for backboard practice. There's tons of stuff available out there just on backboard drills and games.
Carnegie Hall may not be where you want to go, but they don't play tennis there anyway. I think I know where you do want to go and that takes Practice, man! Practice!