Knowing your opponents and how to unravel them is a key doubles strategy in tennis. To understand the mental makeup of your doubles opponents is to understand what will likely lead to their demise. With this knowledge you will know what tactics to use that will cause them to mentally unravel on the court.
Dominator - The dominator is the better player who is bossing their partner around. Learn to isolate the weaker player in this case and 'starve' the dominator of as many balls as possible. This will exaggerate the dynamic and cause them to become unbalanced. The weaker player will lose confidence and feel self-conscious and then the dominator will become visibly frustrated. They will try to compensate and begin pressing and trying too hard, causing their level to drop also. Once you sense this happening you can begin hitting a few shots to the dominator...to confirm your suspicions!
Wanderer - This person tends to lose the score, forget whose serve it is, walk to the wrong position on the court, etc. When you see any of these clues begin playing the ball to them, particularly in a non-pressure situation such as two games all,15-15. Hit a return to them at the net - chances are they are not paying attention. If they are really not engaged they will wander for the whole match. However, beware! Occasionally they will 'wake up' when something exciting is happening, like if the score is close or you're nearing the end of the set. Be on guard because these players can play well under pressure, as they are loose and relaxed. Ignorance is bliss!
Socialite - This player is really in it to get out of the house, meet people, exercise, and have a good time.They will try to engage you in chit chat before the match, during the warm-up, and also during the match, particularly at change of ends. Plan for how you would like to deal with this scenario - perhaps reply politely but be very brief. If it persists you could say something to the effect of "I'm really enjoying the game right now - let's chat after the match." Having a plan will prevent you from being distracted or frustrated by their behavior.
The Shark - This player is an experienced competitor. They may not have the prettiest strokes but they are crafty and they know how to get the job done. They will look for any advantage they can get. They will try to break down your mental game. They may verbalize a few injuries they have, they can stall (shoe laces, injuries, bathroom breaks, and numerous ball bounces), they may not return balls to you for your serve or hit it to the other side of the court so you have to walk to get it. They may continually ask you to go and get balls for their serve. They may tell you how well you are playing to try to distract you, and they may also question your calls, ask you to call out the score, or other things of this nature. If you let them under your skin you are done for! Stay calm. Know that they feel threatened by your play and take this as a compliment. If you weren't such a good player they would not need to do this to win. Use your time between points to focus on yourself, keep good eye control, avoid looking at them and just play the ball.
The Negative Nelly - This player is constantly critical of themselves after points. They always have something negative to say and their body language reflects this. Make sure this player sees a lot of balls coming at them - this can break a team apart. If you don't seize the opportunity by hitting to this player you will allow them the time they need to cool off, and once they regain their composure the level of their play will improve also.
The Exploder - The same thing that applies to the Negative Nelly applies for the exploder. While the negative Nelly tends to internalize and implode, the opposite is true of the exploder - they tend to externalize their frustrations! Direct traffic to them when they are making a lot of noise.
The Crumbler - Look for signs that one player is feeling the pressure more than the other. This player usually starts really hot and is not struggling. Then when the match heats up they call "yours!" on big points instead of "mine!", they let shots go uncontested - particularly big serves or middle volleys - they stop coming to the net or stop poaching, they follow their partner around, clinging to them for support. These players have stopped believing in themselves - make sure you hit to them as much as you can, especially on big points!
When you understand the mental makeup of your opponents you understand the vulnerable areas of their mental game. Be observant and you will quickly identify the type of players you are up against, and the obvious strings to pull that will make their game unravel!