Many players do lots and lots of forehand footwork drills. This allows many of them to dominate the table with their forehand. But there's often a missing ingredient here - backhand footwork.
Backhand footwork is similar to forehand footwork - you need to learn to move side to side as well as in and out. For example, a coach or partner simply hits the ball side to side to the backhand side, one toward the middle, one to the corner or wider. The player moves side to side, playing backhands. Players who don't do this often have trouble covering the backhand side effectively. They can move all over the forehand court fluidly, but on the backhand side they are in trouble. Often this means either weak and erratic backhands, or wild swats.
Often coaches don't work on this much. Why? First, the forehand tends to be the stronger shot, and so coaches and players stress that - and so do lots of forehand footwork drills. Second, many forehand footwork drills incorporate backhands as part of the drill, and so they do get some backhand footwork practice this way, and so think they are doing sufficient backhand footwork drills. However, most of these drills only cover moving from the forehand side to the backhand side, not just moving around on the backhand side itself. Third, by the time players reach the intermediate stage they have developed forehands and so are doing lots of forehand footwork drills - but often the backhand isn't as developed, and so coaches have them focus on continued technique development rather than moving about playing backhand. Many intermediate players are making the transition from normal backhand drives to topspinning their backhands, and coaches are reluctant to have them work on this and do footwork at the same time. (This one doesn't apply to coaches who introduce forehand and backhand topspin shots to developing players at about the same time, as more and more modern coaches tend to do.) And fourth, by the time the player does have a solid topspin backhand, both the coach and the player aren't in the habit of doing backhand footwork drills in their sessions, and so they just don't do them.
All this can lead to a weakness in the player's game as they don't move around as well as they could in covering the backhand side. This is a problem as the backhand by its very nature is a more cramped shot, with the body in the way, and so being able to move about and attack with the backhand is key.
Besides side to side backhand footwork, you can also try in and out. Ideally, learn to topspin both, but especially the one from off the table. You should also do random backhand footwork, where balls are played randomly to the backhand and you play aggressive backhands. You can also have your coach or partner attack randomly to your backhand so you can work on your backhand blocking footwork, or perhaps topspin defend from a few steps back.
Eric Owens attributed his upset win over Cheng Yinghua in Men's Singles at the 2001 USA Nationals to backhand footwork drills. Learn from the champions!