...honestly it's a mystery how his power works. Sometimes a survivor will stare straight at you and they're unable to reveal you, or they can reveal you when you're completely hidden behind a wall. It can be really buggy so there aren't many tips apart from try and refrain from activating stealth mode when you're in the open or straight after you've hooked a survivor, because they can also reveal you
Try not to make yourself obvious so bright cosmetics like the white, red, blue shroud are not recommend it. Try to stay behind cover when traversing the map. Remember your map layouts and tiles so you can walk around a lot easier.
That's just my advice :P
This might sound odd, but the best way to get better at any killer is to get good at survivor, or at least decent enough to know where to go to be safe. The point is to understand their perspective.
As an example, consider that while working on a gen, most survivors will be watching the larger areas of the map if that gen is near a wall. So, if as ghost face you are scaling the perimeter of the map with night shroud active, and you come up on a gen ebing worked on. Chances are survivors aren't watching the wall behind them, and instead they're looking into the open, waiting to see any movement at all in the distance.
With gens in the center of the map, it's a bit harder to stay hidden, because Survs have a 3rd person perspective that can see over obstacles.
A lot of people who play ghost face rely on things like sloppy butcher paired with nurse's calling; it's really effective.
Also, consider peeking around corners from far away. You are smaller and less likely to be seen. You can stalk from pretty far, too, btw.
Also, consider using your power to mind game, and not just stalk people. As soon as the survivor has lost sight of you, activate night shroud and hide behind something, sometimes they will look for you, or think you left; you could run the other direction to cut them off too, or do the double fake and keep running in the same direction you were running in.
When you're running around a loop, if the thing you're running around is high enough, crouch just before you switch directions to mind game; sometimes people will screw up their pathing around the loop trying to tilt their camera up to catch a glimpse of you. Which can give you just enough time to catch up to them.
During a chase, if you hit a survivor, and hear a gen nearby being actively worked on. Activate night shroud and let the injured survivor run away, while you go back and stalk the person on the gen, who might assume you continued on with your chase. Sometimes this backfires and the injured survivor will see what you're doing and expose you.