I was watching a program about driving where they tracked eye movements of amature and professional driver on a course - basically while the novice's eye movements were all over the place, the professional focused in on specific points on the course.
I realized this is perhaps a big difference between many good and bad players in many sports - e.g. snooker (novices look at the target ball) football (pro defenders look at the hips rather than the feet) golf (novices take their eye off the ball) even fps games (novices dont look at the crosshair) and the list goes on...
so - to all you pro players - where do you look?
1. when you are playing the shot, e.g do you focus in on the shuttle?
2. when you are recieving, i.e. trying to read the player
for me and a club level player - i find myself messing up shots because I am watching the other person come into the net for example, I think this should be left to the peripherals.
In the moment of the racket contacting the shuttle, of course you need to focus on the shuttle but before the shuttle comes to you, ideally you could check for open spaces or already have the idea where the weakness of your opponent is.
Many "normal" club level player tend to relax after a very good shot and has the idea to win that rally already but we all know the rally only finishes after the shuttle hit the floor only. Also the lack of technique, no tactical awareness, playing against much better/faster player or not able to anticipate, many tend just to hit the shuttle without thinking of placement.
If I play against a weak player, you sometimes already know by attacking their backhand, there would only be one weak reply and normally I would sneak forward to the net area to make the kill.
When I receive the service, I will try to focus on the wrist movement of my opponent and try to read where they play but many advance player could change direction of the wrist in the last moment or trick you with their body movement but you can only get better by playing more against such player.
For me, I have been punished a lot of times when people play drives to my forehand or backhand and I just play the straight drop return. Because of that my opponents would always anticipate the straight drop and be ready.
Now, I just use my peripherals and better footwork to get there faster I guess, and I see the movement of them covering the straight so I hit it cross court. For overheads, I also use my peripherals to glance at where my opponents are and then I focus on the shuttle and my hitting stroke.
I find it hard to read the person serving to me, but you do pick up on some things like when they're about to flick you. I know I've face opponents that do the a leg twitch or a noticeable back swing when they intend to flick? I pick up on that I guess. But if its low serving I don't really lol
On the other hand, when I am serving, I try to look for patterns and see what kind of shots they play and try to get that 3rd shot.