Throwing a hook
In order to throw a correct hook, you need to first figure out the technique that goes into it.
Firstly you need to go ahead and focus on the area on your opponent that you want to hit. Once you do this, you can do the next few steps.
After figuring out where to hit your opponent, based on what hand you use to write, come from the opposite end. For instance right handed people will come from the left.
While coming in, put your chin down, so that it is now on the inside of your left shoulder (for right handed people)
Now turn your hips and toes in the direction that you were going to punch in.
Before making an impact move your hand, so that when you impact with your opponent, you hit him with all four knuckles.
In order to really get good at throwing hooks, you need to spend a lot of time in the gym, working on your speed and punching power. This is going to take a long while, and will require you to go ahead and stay rather dedicated to the whole thing. Any slacking off will not be acceptable, since any lack of technique in the ring could cost you the match.
In order to get the most behind each punch, you need to work with weights. Now working with weights will help you build power and even speed to a certain extent if you do everything right.