They have the similar form to squats. Knees not past toes, Ass down and out, keep back straight or better yet arched and abs tight. When lifting the bar off the ground, it is ideal that the bar is as close to you as possible. Here's a link for an animation.
Keep your back arched through entire motion (helps target hams) and slowly lower the bar. I prefer to have knees slightly bent. If you've never done this, be prepared for a nice stretch.