Here are five serves that any serious player should have. Some you might use regularly; others you might use sparingly for a few free points each game. Many long-time players, even top ones, continually handicap themselves by not having the needed variations that would finish off an opponent – and often they don’t even realize it, and so give away a few points every game that could be “freebies.” Since there are three long serves (#1 below), and backspin/no-spin is two serves (#2 below), there are really eight serves everyone should have. But I like to group the deep serves together as “The Three Primary Long Serves” players will remember them when practicing serves, and when playing a match.

1. The Three Primary Long Serves, served from the backhand corner, often forehand pendulum serves.
   1. Deep crosscourt breaking sidespin serve that breaks away from the receiver (to the wide backhand if a righty serving to a righty). These serves throw off a receiver’s timing and often leave them lunging for the ball. (This doesn’t mean you should only do deep sidespin serves that break away from the receiver, but they are generally trickier to receive than ones that break into the receiver.) At the intermediate levels, a serve into the forehand that breaks away from the receiver can cause great difficulty, especially if not over-used. At the more advanced levels, that’s not effective and so breaking serves are mostly into the wide backhand.
   2. Fast no-spin at the elbow. This serve is put in the net so often it’s a mystery every player doesn’t develop this serve. It’s the single most effective “trick” serve up to about 2200 level (which is pretty advanced) – almost a guaranteed point or two every game if done properly. Against players who cover the middle with their forehand the serve might be more effective into the wide backhand, or down-the-line if a righty serving to a lefty (or vice versa).
   3. Fast down-the-line (to a righty’s forehand). Also effective crosscourt if served righty to lefty or vice versa. Many receivers try to cover more of the table with their forehand against deep serves, and so are vulnerable to sudden fast serves to the forehand. It also draws them out of position for the next shot. For righty vs. lefty or vice versa, there’s a big angle into the forehand, so it can be even more effective unless the receiver shades over to cover that wide forehand – in which case they may be vulnerable to a fast down-the-line serve.
2. Short backspin/no-spin to the middle. By going to the middle, receivers have no extreme angles, and the server has less ground to cover on the follow-up. By mixing in backspin and no-spin, receivers often put the backspin in the net, and pop the no-spin up. It’s important that these serves be very low to the net, and bounce twice on the far side if given the chance. If serving no-spin, use a vigorous motion as if serving with spin – you must sell it as if it’s a backspin. If serving backspin, use less arm and more wrist so receiver will see less motion and think it’s no-spin.
3. Backhand-type sidespin from the middle, served short to forehand or long to backhand. Many players are more comfortable receive short serves with their backhands, and have even more trouble with backhand-type sidespin short to the forehand, which breaks away from them, and can be awkward to receive since to compensate for the sidespin they have to aim down the line, which is trickier with the forehand on a short ball. By serving from the middle of the table, it gives the server an angle into the short forehand that cause even more trouble, while putting the server in perfect position for the follow-up shot, which usually comes to the forehand. Receivers often “cheat” and move in to cover this serve, even receiving it with their backhand – so be ready to use the same motion and suddenly serve out to the backhand, catching them off guard.
4. Sidespin-topspin serve that looks like backspin. This is the serve many top players use to serve weaker players off the table. Their racket tip is moving down at contact, so the serve looks like backspin, but the racket is rotating about its center, and so the bottom is moving sideways and up – and so the serve is side-top. Receivers often push it, and it pops up or goes off the end. Against stronger players, if you over use this serve they can attack it – so don’t over use it, unless you are a counter-driving player. Use it sparingly, and it’s free points.
5. Both types of sidespin. Some receivers are good against one type, not the other. Many players can only serve one type of sidespin effectively. Not only should you be able to do both, you should have motions where the receiver doesn’t know which you are doing until you start your forward swing. The most common method is forehand pendulum and reverse pendulum serves. But you can also do backhand regular and reverse serves and forehand tomahawk and reverse tomahawk serves. 

One of the keys to improving is getting a good practice partner. Usually these are two players who are roughly the same level. But it's more important that they both want to improve, are willing to work together, and are regular to train on a regular basis. The more they train together the more used to each other they get, and the better each plays in these drills. This leads to both players' levels escalating up – an upward spiral to excellence! (Here's my article on How to Play and Practice with Weaker Players.)

I want to emphasize how much better you play when you drill with someone regularly – you get used to their shots, and your own shots become more and more natural and consistent, as well as more powerful. Some might think this is artificial, since you are playing against the same player and shots, which isn't what happens in tournaments or leagues. But the key is how much this type of drilling develops your foundation. (This doesn’t mean you only practice with one player, but if you are able to practice with multiple players, the more you hit with them the better you’ll drill with them.)

Players still need to practice with and play others with different styles, especially matches – that's imperative - but drilling with a good partner (or partners) develops the foundation that's so important to developing your game.

Once you find someone to train with regularly, take turns with the drills. But remember that in any drill, both players are doing the drill. If one player is doing a footwork drill to the other's block, then the other is doing a blocking drill. Players not only need to learn to move and attack, but also to control an opponent's shots. And remember even blocking is a footwork drill – you need to step to the ball, not just reach.

Don't forget to get a box of balls and do some multiball training! (Here's my article on Multiball Training.) Multiball training makes up about 1/3 of the training of world-class players. 

Many players have great difficulty looping slightly-long balls, especially with the forehand. These are usually serves or pushes that go only a little bit off the table. Most players push them back – and since the ball is relatively deep, they can’t get a good angle nor can they rush the opponent with a quick push, and so their return is ineffective. The solution, of course, is to loop these balls. (And the nice thing here is that when you read these balls right, they are easy to loop very aggressively.) How do you learn to do that?

Here are three tips for learning to forehand loop against slightly-long balls. (Tips 2 and 3 apply to the backhand loop as well.)

1. You need to be very close to the table, with your head directly over the end-line. This allows you to look down on the ball, making it much easier to see if the ball is long, as well as easier to time it.
2. Realize that you can loop a ball even if it is actually slightly short, i.e. the second bounce would be on the end-line or even an inch or so inside. You simply stroke aggressively over the table with a slightly upward stroke. Once you realize this, you’ll see that balls that seemed unloopable are actually very loopable. (You can go over the table even more with the backhand loop, by using more wrist. In fact, a backhand banana flip is essentially a loop done over the table.) Some worry that they’ll hit their hand on the table, but if you are aware of where the table is, you just stroke slightly behind or above it. If you can contact a small, moving ball, how hard is it to avoid hitting a large stationary object? (In 40 years of play, I don’t recall ever hitting my hand on the table while looping.)
3. Practice! How do you do this? Have someone feed you multiball backspin where the ball is only slightly long, or do it live where you serve and your partner pushes the ball back slightly long. You’ll have to adjust to each shot as some will be longer, some shorter, including some too short to forehand loop. Get your head over the ball (see #1 above), recognize that you can loop balls that you didn’t think you could before (#2 above), and loop those that are loopable. At first, if you think the ball is unloopable, let it go. You’ll be tempted to adjust and either push or flip, but letting it go is the only way to get true feedback. Watch it and ask yourself, “Could I have looped that ball?” Often the answer will be yes. Eventually, with practice, you’ll be able to judge this, and then you can stop letting the ball go, and practice either looping the loopable ones, and pushing or flipping the shorter ones. 

Do you keep a table tennis notebook? I did for years, and I recommend you do as well. I used a steno notebook. From front to back, I would take notes on my own game - what I was working on, what drills I was doing, what worked and didn't work in matches, etc. On the other side - back to front - I kept tactical notes on opponents. When the side on me was filled up (it usually went first), I'd get a new notebook for my game and start fresh. At tournaments, I'd bring past notebooks (with the ever-growing notes on opponents), and would be ready against any opponent I'd ever played against.

After doing this for perhaps a decade, I realized that I'd been doing it so long that notes about opponents I’d played were all in my head, and that I no longer needed to consult my notes to remember them – but the very act of writing them down made it easier to remember. I eventually retired my notebook in regard to tactical notes against opponents – though I sometimes would write down the notes as a memory aid, and then put them aside – but for years afterwards I kept notes on my own development and what I needed to do to improve.

These days you might use a smart phone for such notes, or go old school with a steno notebook. It still works!

While I no longer have a notebook for my game, I still keep notes on regular opponents of players I coach, which I jot down at tournaments and later type up in my coaching files on my computer. When I show up at major tournaments I bring these top secret printouts. 

Returning serves is all about ball control. In a rally, the incoming shot is usually more predictable than a serve, which normally has a much wider range of variation – topspin, sidespin, backspin, at all speeds and placements. To return serves, where the incoming ball is far less predictable, it helps to shorten the stroke to maximize control. This cuts down on power, but the shorter backswing gives you more control. (Just as with other strokes, the backswing and follow-through should still be about the same length.) The exception here is against a deep serve where you read the ball well, and so may use a normal loop stroke.

Watch the top players, especially against short serves. Do they rip the ball when receiving? Only occasionally, and when they do it’s because of their extremely high level of play, or because the opponent made an error with their serve (a slightly long or slightly high short serve, or a “surprise” deep serve that doesn’t catch the receiver off guard). Whether they are pushing (short or long) or flipping, it’s all about consistency, control, variation, and deception. And for that, they shorten their swing and gain in all four categories.