Doubles Tip for the Server #5: Kick serves high and wide to the receiver's backhand on the ad side. No one likes to hit high backhands, especially with one hand. It's difficult to get much power or topspin on a high backhand, and a return lacking these attributes is usually relatively easy to pick off at the net. A twist serve is ideal, as it kicks high and toward the receiver's backhand, but a topspin serve, which is easier to produce, also works well.
Doubles Tip for the Server #4: Use a heavy slice serve on the ad side to curve the ball behind the receiver's partner. This tactic is great fun and can be extremely effective, but you don't see it often, because not many players develop a heavy slice serve that curves enough to work. It's not an especially difficult serve to learn, and it has many other tactical uses, especially in the wind. The receiver's partner usually stands within a few feet of the T; if you aim a heavy slice serve near the T, it will curve enough that by the time the receiver hits it, his partner will be right in front of him, blocking most of the court.
Doubles Tip for the Server #3: Jam tall receivers, using direct aim, slice, and twist. The taller the player, the farther he has to move to make room for a normal swing at a ball coming into his body. If he doesn't get far enough from the ball in time, his swing will be cramped and usually weak, setting up an easy ball for you or your partner to put away at the net. You can jam him by aiming straight at him with power or by curving the ball into him with slice or twist. A jamming serve often has the added advantage of surprise, because most players usually aim for the corners.
Doubles Tip for the Server #2: Serve up the middle to the receiver's backhand. For most players, the most difficult return in tennis is the inside-out backhand used to hit crosscourt on a serve up the middle. Against right-handers, you'll use this serve on the deuce side. Most doubles players stand closer to the center mark on the deuce side than they do on the ad side in order to make placing the serve up the middle easier. If you can hit a twist serve, it's easiest to place up the middle, and it has the added advantages of kicking high and curving to the receiver's left.
Doubles Tip for the Server #1: Come in behind your serve. Although serve-and-volley has become rare in singles, it's still the standard and best tactic in doubles. With your partner at net, ready to put away any returns she can reach, the receiver's job is already difficult; your coming in makes it all the more so, while your job as volleyer is much easier than in singles, because you have only half of the court to cover. Most doubles points are won at the net, and with you and your partner there behind a good serve, you have a clear advantage. Retain your flexibility, though, so that if your opponent starts hitting short returns that land at your feet and force you to hit up with a weaker volley, hang back now and then, and put that short ball away with an easy groundstroke; if your opponent never knows when you'll do this, he will never be sure how to return your serve.