Communication Tips

To form an effective doubles team, both partners need to communicate on court. Even in singles, it's important to communicate to avoid disputes.

Scouting

If you have to play someone in a tournament, ask people who know them about their game. Often you'll get advice like "he really hates..." or "he can't handle...", even from their friends! Even if someone doesn't want to tell you about your opponent's weaknesses, they'll usually tell you about their favourite shots or their playing style.

Singles

Always call balls that are out, even if you also give a hand signal. That reinforces that you are sure the call is right.

While calling the score before each serve might be overkill, it is a good idea to call it occasionally during each game:

• When the score gets tied up, especially if your opponent has won the last couple of points. They may forget about the points you won earlier.
• When you have game point, just to make sure they don't argue the score after you think you've won the game. Don't announce "game point" or "match point" though -- that's often considered rude.
• When you've won one or more points through luck or by your opponent making a really bad play. People seem to block those things out of their memory and often mix up the score.
• After any kind of dispute or interruption, like a let due to a ball rolling on the court. Calling the score is also a good way to end a dispute, signalling "I am not going to change my call, this is what the score is...".

If you are not serving, it is often considered impolite for you to call the score, so ask the server (even if you know the score) or pose it as a question, e.g. "is that forty-thirty?".

If you feel you got a bad call, let them know without accusing them. For example, if they call your shot out, ask "that was out, right?" or "was that out?" (as if you didn't hear their call). If they made an accidental bad call, that gives them a chance to reverse it without losing face. When they reiterate their call -- and they will, the other 99% of the time -- accept it without further comment. If they are just trying to get a slight edge and are not out-and-out cheaters, knowing that you are suspicious but still polite is often enough to head off bad calls later in the match.

If your opponent is doing something like footfaulting or distracting you, point it out once, quickly and politely. If it continues, ask immediately for an umpire (even in the first round!). Either they are doing it on purpose or it is an unconscious habit, so it's better for an impartial person to ding them for it.

Doubles

After the warmup, before you start the match, trade observations about the playing style, strengths and weaknesses of your opponents.

Decide beforehand who will serve first, and what you'll do if you win or lose the toss. No sense in having to think about it just as the match is about to start -- that's a distraction. If one of you is feeling especially good or bad, or there is some unexpected condition like the sun shining in your eyes, you can make a last-minute adjustment.

When your partner is serving, you as the net player get a much better sense of how effective their serves are:

• If they are missing too many first serves, making it hard for you to poach or setting your opponents up for an attacking return, ask them to concentrate on raising their first serve percentage. (Don't ask them to "make sure you get this next one in" as that kind of pressure can be counterproductive.)
• If they are hitting ineffective serves, for example to an opponent's stronger side or wide serves that let them pass you, ask them to try a different tactic.
• If your partner is successful with a serving tactic, remind them periodically to keep using it.
• On a big point, or if you want to poach, ask specifically for a serve down the middle or out wide, or flat, kick, etc. based on what has worked the best. Typically, against right-handed opponents, the most effective serve to call for is a high kicker down the middle in the deuce court, or a hard flat serve down the middle in the ad court.
• You can signal your intention to poach or apply some other tactic (e.g. for your partner to serve and volley, or to hit a certain kind of return), either with a verbal signal or a hand signal. If you use a signal that your opponents are aware of, like flashing a hand sign or huddling before the serve, make sure you do it in situations where you don't intend to try any special tactic, so the opponents won't anticipate your play. You can use non-obvious signals, such as agreeing on a phrase like "Let's go!" to mean a set play.
• All of these discussions are especially important if you are losing a lot more points on one side than the other. For example, if your partner keeps missing their first serve or having trouble serving and volleying on the deuce side, you may be much more aware of that pattern than they are. Point it out, but in a positive way -- "let's try a surprise tactic" of a kick serve, serving and staying back, and so on.
• If you perceive that you are losing a lot of points, ask your partner's advice for your serves, returns, and so on. They may see what's wrong but be too polite to say. If they don't have any advice, at least you'll know they aren't secretly fuming at some dumb tactics from you.

If a ball comes down the middle and you think you should take it, call "mine!". Typically you would do this if you are closer to the ball, if you are closer to the net, or if the ball is coming to your stronger side and your partner's weaker side.

If you know you can't reach a ball or that your partner has a much better play, call "yours!" or "help!". A frequent mistake in doubles is to wait at the net on one side while your opponents hit a drop shot to the other side that you could get to. That verbal signal can alert you in time to cross over and retrieve the shot.

If a ball gets over your head and your partner calls for it, allow them to take it 95% of the time, even if you think you can get it. They will be crossing behind you, so unless you hit a winner you will both be on the same side of the court and effectively out of the point.

Conversely, if you can see that your partner can reach a lob or make a running get, but they might misjudge the ball and let it go or slow down, encourage them with a phrase like "you've got it!".

If your partner is too hyper, encourage them with some calm words. If they aren't putting out 100% effort or they seem intimidated, encourage them with a call to action. If they are distracted from the game, for example by obsessing about being so far behind or only needing one more game to take the set, remind them to just focus on winning each point as it comes along, and if you can keep doing that then eventually you'll win the match.