I was playing on a mixed doubles (first time with this team) team years ago and the captain hadn't decided the final line-up until
I was paired with this young lady who had good pace on both ground strokes and could move well laterally. I had only hit with or against her a few times in practice (more later on practice).
However, our opponents didn't meet each other just the day before and we had our hands full. I noticed my partner wasn't coming in, even when I may have had enough time to go get my car and park it in her service box. Our opponents weren't obliviously to the fact either.
During her next service and between serves I walked back to her and invited her to come up to the net. "I don't play net," she said, which up to this point was quite obvious. "I asked what side of the court you preferred. Not which corner," I replied. She laughed. "It's fun up here. Come on up," as I returned to the net.
She did and although we lost the match our odds of winning increased dramatically. She actually said she had fun playing the net.
I'm not just taking a jab at women or some of the oddities of mixed doubles, I had a 4.0 male partner tell me the same thing one time.
While playing Moose League, a bunch of tennis players rotating after every set, where the play could be as casual or challenging as possible depending on your partner and opponents, I was paired with another no-net player. I knew this, taking advantage of it with drop shots and acute angle shallow returns when on the opposite side of his net. He had no problem covering the court except for that area that begins about two feet inside the service box and continues to the net. It's as if there is some imaginary crime scene Do Not Cross tape up there somewhere. I have seen him come close to the service line to take a shot and then retreat to the baseline for no obvious reason.
On this day, although I do take my play serious (whatever) and not the wins or losses, his lack of net play was getting under my fuzz (skin). So I said (Although this is not entirely true, but much more so than singles play.), "Doubles tennis is won or lost at the net."
His reply, "That's for the pros." Okay, a futile attempt by me. Doubles is not simply four people playing singles on a wider court. It's a different type of play than singles.
Some of these same no-net players don't have a problem at all hanging out up there during their partners service, which tells me many may simply have a fear of timing and committing to the approach.
Below is a good video on net play and the approach. This is helpful not just for singles, but doubles as well. A friend and I, both primarily doubles players, do a drill similar whereas we hit moderate pace balls near one another and then, after the third shot, the hitter approaches the net to take the fourth shot regardless of being a short ball or not. After that we go for the passing shot or put-away. This requires more attention to footwork, focus and control (not running through your shot), which is all good as long as you don't get it in your head that you are going to approach the net every time the opportunity is not afforded.
We alternate who comes in as this can get quite exhausting, but it can help you with the burst of speed required to get to net quickly.
You may wish to do this drill using only half-court if doing so for doubles play, considering any shot to the opponent's area crossing his or her service box out. We have also done it where all shots must be cross-court into the opposite half court.
Of course, if you can court four players for the drill, you have a more realistic situation for the drill. Or, you can hire a teaching tennis pro and take advantage of some group drill pricing. Go to Teaching Tennis Pros.