I prefer how I was taught, which was to follow what happens naturally/anatomically (ideally in order to maximize power transfer).
Try this:
Hang your hand at your side, then bring your hand up so your arm is bent at 90 degrees, keeping your elbow fixed at your side...and make a fist.
Look at your fist - your fist should be thumb up, pinky down in relation to the floor.
Now begin slowly raising your elbow out and up until your upper arm is level with your shoulder, and observe what happens to your fist. As your elbow goes up, your fist steadily turns until when your elbow is even with your shoulder, your palm is now facing straight down.
Thats more or less telling you what is the correct form to throw your hooks anatomically and with max power.
Basically, the angle of your fist changes depending on whether you are throwing to the body or the head in order to maximize power.
If you are throwing more as a deceptive hook (i.e. where you need distance and not power) then you can get more range by turning the fist /palm in/ to the head...but its a sloppier hook with less power since you will extending it beyond its ideal range (you are extending the elbow past 90 degrees, and relying more on your bicep for stabilization/power transfer instead of bone/ligament).
Thus, I only throw a hook like that to setup something else, i.e. a low kick to the leg.