Lots of different opinions here - none wrong.
Here's some shit that I've learned and used to make my left/lead hook reasonably fast and powerful.
First, find out if your hook is more effective with palm toward you or palm to the floor. For some people it makes all the difference in how the wrist is rotated when the punch is executed.
Second, for the love of God, find someone who knows what they are talking about to show you how to properly throw a "lead hook" as opposed to a "rear hook". And when I say properly, I mean all aspects of the punch: forarm, arm and shoulder movement/placement, legwork, torso and hip movement/placement and, perhaps most importantly, HEAD AND CHIN PLACEMENT. FFS just the other day I was doing heavy bag drills with a guy at the local gym and he was going on about the power of his hooks. Thing of it was that at the end of his punch his feet were awkwardly placed, and even better, his chin was beautifully exposed during and after the punch: bad foot placement + exposed chin + missed hook punch = "Hey buddy! You okay? I knocked you down. You okay?" I didn't say anything and won't until we have a few sparring matches.
Third, and this was/is something that I put myself through because I was unsatisfied with the raw strength of what I call a "shoulder hook", which refers to the power you generate strictly from the hook motion of the punch caused solely by the movement of your entire arm by your shoulder muscles. A lot of folks have weak "shoulder hooks" yet when they stack foot, hip and torso motion, they come out with a reasonably powerful punch. Problem is, of course, when you're in close or you start to gas and don't have the mobility you did when you were fresh. There is no substitute for having strong, individual elements behind your complex motions. In otherwords, attack the weakest elements of your punches/technique and make them stronger.
To improve my lead hooks I stood at a comfortable distance from the bag from which I could throw a solid lead hook, froze myself in a protective stance, and threw consecutive hook punches, focusing on isolating the entire movement to that of a shoulder exercise. Whenever you do a bag drill, do this a minimum of 1 round each time. I did this for my lead hook in orthodox and Southy stances, and the muscularity and strength of my shoulders improved quite noticeably. Now, I can throw an isolated shoulder hook and feel reasonably satisfied by the power I generate on that alone.
Fourth, unless you're athletically gifted with better than average speed, a lone, lead hook is a risky venture. Practice throwing a jab-hook double, adnauseum, until the muscles that power the transition between the punches strengthen sufficiently to make it a comfortable motion, rather than an awkward one.
Anyhow, this is just stuff that has helped me improve my speed, power and technique. Everyone's body is different, so find out what helps you. Don't be lazy.
