To improve your doubles game, try playing skinny singles. Skinny singles is one of the best drills because it emulates the strategy and play of doubles, but you have the opportunity to play every shot and work on your skills on every shot. Also, with a smaller court, you are forced to focus on your placement of shots.
To play skinny singles, you need yourself and one other player. You can play skinny singles straight on or crosscourt (be sure to try all directional combinations!), but the key is that you will only play in half of the court on each side of the net (so the boundary lines will be the centerline and the applicable sideline), with regular scoring and a similar strategy as doubles.
Bottom line – Play skinny singles to work on your doubles game!