Number One: Over hitting your forehand volley
The Fix: Do not take such a large backswing. Think of your forehand volley as 80% footwork and 20% your racket. Everyone naturally over-hits their dominant side. Keep your racket inside your peripheral vision and keep your body moving through the shot. That way the mass of your body will help add power with control to your forehand volley. Also, it is very distracting and intimidating when your opponent sees you moving forward.
Number Two: Under hitting your backhand volley
The Fix: Typically, a player will under hit or push their backhand volley. They will have a difficult time adding pace to a ball which is coming slowly. Do not be afraid to take your racket farther back, (a bigger shoulder turn). When you first try this, focus on hitting the ball harder, rather than worrying about the ball going in. After you master this, then start moving your feet through the shot as you hit. This will also help you add more power.
Number Three: Under hitting your overhead
The Fix: Very typically, players will hit their overhead hard in practice, but when the match actually starts they will guide or push the ball. Let us say that you receive at least six overheads in a typical match. If you missed every one of these overheads, it will not be the reason that you lose the match. If you made all of them, it will get you off the court sooner. So, when you receive a lob, think aggressively and positively. Picture yourself being successful. Reach high and accelerate your racket speed. Take all thoughts of missing or whiffing it out of your head.
Good luck on the courts!