Talking about the mental game of tennis in one page is ludicrous; nevertheless, there is one step you can take.
Example: You begin a match and realize that your opponent's forehand shots seem slower than her backhand. They're easier to play and allow you to hit the ball harder. Her forehand is her problem. Solution: hit to her forehand whenever you can.
HOWEVER...
Your shots are inconsistent—five out of every ten shots are going where you don't want them to go. (Sadly, that's the average of the top fifteen (!) players on our ladder.) Your strategy is worthless: you know what to do, but you can't do it. That's why fooling around at the net or working on a lot of crazy shots is a waste of practice time. Groundstrokes count, and count, and count....
In doubles, the most important shot is the return of serve. Any doubles player who masters that will be a desirable partner, even if she can't play the net at all.