The opposing net player poaches a lot... How do you stop him? 

Here is a situation: you and your partner are playing against a team whose net player loves to intercept your serve returns and puts them away most of the time. He is very quick at the net and all your attempts to keep the ball cross-court away from him end up in volley winners from the other team or unforced errors from your side.

Solution: 

Hit the serve returns or short rally balls aggressively straight toward the opposing net player.

By doing that you will transmit the message to him to stay put otherwise he’ll get passed down-the-line/alley. 

It’s very important to do this tactic at the first point of the game. You can try on the second one too; he might think that since you did it once, you will not do it two times in a row… surprise him! :)