The only time I hook the ball is when I really don't have any other options. For example behind trees, or a slopping fairway from left to right. Or maybe the green goes back to the left. Having that decided, now this is where I start to really have to think about what I have to do in the swing, to get the ball to go from Right to Left. Most of the time it does go with the correct flight however it doesn't always start out at my intended target, so that means I will finish wide of the flag anyway. Therefore I don't tend to hit too many draw's or hook's.

All that said now I will try to explain what I do to hit a Hook or Draw.

• First of all I put the ball further back in the stance than normal.
• I try to swing the club on a path that I want the ball to travel at. 
• The best and easiest way to hit is to just release your hands. By this I mean to rotate your left wrist through impact to the left. The club must release earlier than in a normal shot because you need the ball to be spinning right to left. 
• If you open the club face at address this will help with an early release. 
• On the practice range try to find a slope where the ball is above your feet to get the correct swing and release.

Remember to practice this  shot on the range so you will know what works for you.