Hitting a flying rennis ball, especially when someone is trying to win a point against you, is a lot like an assembly line process with many sub-operations all coming together at the right time to make a well finished produce. In this case, the product is a well hit ball- back to the opponent's court.
You can divide the process into court sense and tactics, getting to the ball, setting up in correct position, and stroke mechanics. If any one aspect of the process fails, then you experience product failure-- sort of like in "I Love Lucy" where she is trying to make chocolates and gets behind and then there are bob-bons all over the floor. Substitute "balls" for "bon-bons".
Start with watching the ball. Watch it go from your side of the court and arc over to the opponents side. While the ball is flying, you should be adjusting your position to somewhere in the center of the most likely area of returns.
How do you know where the ball is likely to return-- court sense. You can get this fron experience, but also from watching other players, and from reading books about strategy, ball placement, court angles and percentage play. I recommend you go to the bookstore and find something along these lines.
Now, the ball is coming back-- watch it leave the opponent's racket and begin to make further adjustments. Keep your eyes on the ball and move in as direct a path as possible toward the spot where you can set up for your stroke.
Now you are there, waiting, knees bent, weight on the rear foot, racket back-- ready to execute the stroke. Still you are watching the ball and making final, small, shuffling corrections.
The ball is bouncing up to the contact point. You are poised, almost spring-like. You begin to shift your weight- moving your weight and energy forward. Mentally, you visualize the path your racket must take through the ball in order to land where you intend. You follow that path with your racket- watching the ball intently and hit the ball to an intended spot that will give you the best advantage. That is tactics- and the same book should cover that, as well.
Watch the ball arc over to the opponent's court... and repeat.