Snatch

Stand with your feet shoulder-width apart and grip the barbell with a very wide "hook" grip, keeping your hips low and chest up.
Pull the bar off the floor by driving through your heels, keeping the bar close to your shins and your back flat.
As the bar reaches mid-thigh, explode upward by extending your hips, knees, and ankles while shrugging your shoulders.
Quickly drop into a deep overhead squat, catching the bar with arms fully locked out above your head.
Stand up completely while holding the bar overhead, then lower the weight to the floor in a controlled manner.

Tips

Keep the bar in contact with or very close to your body from the floor through the pull, so that it travels in a straight vertical path rather than swinging away from you.
At the catch, lock your elbows out fully and press up slightly into the bar so the weight is supported by your skeleton rather than absorbed passively by your joints.
Time the shrug and the pull under so that you begin dropping into the overhead squat as the bar reaches its peak height, rather than waiting for it to stop moving.

Letting the hips rise faster than the shoulders during the initial pull causes the torso to become nearly horizontal before the bar leaves the floor, making the later hip extension less powerful.
Bending the arms early during the second pull, before the hips and legs have fully extended, shortens the pulling distance and reduces the upward momentum transferred to the bar.
Catching the bar with the elbows slightly bent rather than fully locked out places the load on the muscles and tendons of the arm instead of transferring it through a stable, straight-arm structure.