Problem: You are at the net when your partner is serving and you really never seem to get a ball to poach and you always get lobbed over.
Solution: Start back 1 - 2 steps from the spot where you normally stand. Wait until you hear your partner serve. Start moving forward very slowly (baby-steps). Do not commit your weight or direction until you are 100% sure the shot coming at you is a forehand volley, a backhand volley or a lob. If the next shot does not come to you, slide back and start the whole process again.
If the shot goes over your head, you will be glad you were not standing on top of the net or moving in too fast and too early.
Remember, it is more comfortable and faster moving forward for the volley (poach) than backward for the lob. Plus, your reflexes will always work better when you are moving forward.
If someone pushes you from behind, your hands will tend to go forward to catch yourself, perfect for tennis. If someone pushes you from the front, your hands will tend to catch you by moving backwards. Plus, from all the repetitions of stopping and hitting ground strokes, your racket will tend to go backwards. So, at the net, the slight forward movement and your starting a little further back to start the point will really help you cover your alley, poach to the center and cover the lob over your head. Thus, you will be at the right place at the right time.
Good luck on the courts!