Signals

In doubles let's face it, signals work. They force players to do things they ordinarily wouldn't do:

poach, fake poach, cross to cover your partner before your opponent figures out what you are doing. It creates confusion and distraction for your opponents; it makes them think twice which is never easy! Fist on the back means fake, open hand means poach, and moving your fingers in a beckoning fashion means come to the net after your serve or return.

Your partner has to be willing to try them, otherwise its better to just play it straight.

Good luck!