Wu,
One thing that helped me was putting the bar in a rack and loading on a bunch of weight. Then get underneath it in the rack position and just stretch your wrists back by standing up. Remember you only want fingertips touching the bar with your wrists up high and your elbows forward. A mistake I see often is guys trying to hold onto the bar tight with their palms especially after coming out of a clean - you need to make sure your hands are just there to stabilize it as it rests across your clavicle.
I don't know how much help I can be with o-lifts, my form is also pretty bad. Can you take video of yourself and put it on youtube?
www.weightliftingexchange.com has tons of footage of olympic weightlifting which is really helpful.