If you have 2 courts (ie. 3 people on 1 court) there are a couple of things:
1: 2 on 1 hitting. Focus on backhand or forehand. The (1) should come back towards the middle and move out to hit a cross court or down the line bh/fh. It's quite tiring and you can just rotate after x number of balls.
2: As a game, there's a game called "Grand Slam". It's singles points. Best of 3 points. If you win 2 of 3 you stay on, if you win all 3 you get a "slam". After all 4 slams have been taken for the year, you move on to the next "season", basically until you get sick of it.