I'm not sure if there is a "proper" way to throw a hook. First of all, you have to take what the lanes are giving you. After that, you should decide what line you want to play or are capable of playing with your shot and/or equipment. Once you're on that line you just need to focus on making good, consistent shots and adjusting when the shot transitions.
Pretty vague, I know, but there are so many variables that play into it. It could be that you're at the stage where you just need to work on consistency, so you're throwing the ball the same way every night. That's probably the most important thing. After that you can try tweaking your release and timing to add or remove speed, revs, axis rotation, etc.
If consistency is your main issue, a coach could help you work out the kinks in your game that are causing it.