A snap hook is more destructive than even a slice--it runs hotter and travels farther along the ground, making it difficult to keep your ball in play.
If you're prone to hitting more than a few snipes, it's likely you're coming up out of your spine angle--your forward tilt toward the ground--as you near impact. Your hips slide toward the target instead of rotating, and your weight hangs back, causing you to release the club early and close the face. This early release and lack of body rotation leads to a hook. Here are two drills to help prevent you from losing your spine angle at impact so you can stop the snap.
1. Widen your stance
2. Grip down