Problem: Hitting too many balls down the alleys.
Solution: Hit in the alleys when your opponent is poaching too often or when you are pulled wide outside the court.
Problem: Trying to move the opposing deep player too much.
Solution: By hitting to the deep player you do two good things. You are not allowing the net player to poach and you are not giving your deep opponent a chance to create an angle. You will make fewer errors just by hitting the ball back to the deep players, thus allowing your partner to poach. In doubles, the majority of points will be determined by the net players.
Problem: You hit your first serve hard, but it seldom goes in and you "baby" the second serve putting your partner at the net in a very vulnerable position.
Solution: On your first serve try to continue hitting hard, but try throwing your toss slightly behind you to gain some spin (control). Many times I try to teach my students to hit a serve not as hard as their first serve, but harder than their second serve. Then I ask them to hit this as both their first and second serve. Later, as they become more confident they can use this serve for their second serve, knowing it will go in. Then they can be more aggressive with their first serve knowing they will no longer "baby" the second.
Problem: You are hitting a lot of volleys but not winning points.
Solution: You are probably moving to a comfortable position, (for example, the service line), and allowing all the balls to come to you. Move to the ball. After every volley move at least two steps forward. You go to the net to win the point, not rally. Spend your life moving forward.
Problem: You are lobbing too much.
Solution: Lob to buy time to get back to the court after being outside or to give your partner time to back up and defend. The first time that you lob and the ball bounces and goes to the deep player, move forward and accept their lob with a volley or overhead. I know teams that lob so much that their matches last so long that no one wants to stay and watch (extremely boring.). Do not let the lob be your primary shot. When your opponent lobs, try to take more and more in the air.
Problem: You come to the net to join your partner and either hit rackets together or you are never sure who should take the ball.
Solution: There is not a rule that you and your partner have to be exactly the same distance from the net when attacking. Keep one player slightly in the lead, maybe one to one-and-a-half steps. The lead partner will be the Captain and have first shot at the ball down the middle. By keeping your partner out of your peripheral vision, you will quit questioning who should get the ball and automatically start taking it while moving forward.
Good luck on the courts!