It is hard to provide specific advice without seeing you play.
Prediction comes with experience. There is no standard rule about where you should stand based on each shot.
General rule of thumb is to:
\- avoid getting caught in the transition zone when the opponent touches the ball. opponent at the net, you need to be behind the service line, defending. opponent at the back, move to the net. this applies to most beginner/intermediate players. it is possible to also defend or attack from transition zone, the more advanced you become.
\- for low bouncing balls at the opponent's back glass, move closer to the net to finish the point in case of a weak return. for high bouncing balls, stand slightly back, expecting a lob.
\- good position to reset at the net is between first and second post. if you are a shorter person, you can stand a bit closer.
\- use the windshield wiper at the net: shot goes to the left corner, you and your partner cover the left and the middle. shot goes to the right corner, you and your partner cover the right and the middle.
\- neutral position at defence is approximately one racket length from the side wall and service line when you fully extend your racket arm. whenever you defend a ball, always reset to this position and be ready.
\- practice doing split step whenever opponent touches the ball. this will allow you to quickly sprint to balls and you will not get stuck and heavy at your current position.
\- always have your racket up and prepare in advance. getting to correct position is one thing, hitting the ball on time is another.
\- rotate your stance in the direction of the opponent hitting the ball.