I think of the clove hitch as two identical loops. The second is placed behind the first. The clove hitch is important for attaching to the middle of a rope. Don't attach to the end of a rope, because it can crawl off the rope and cause injury. Did you know that there's a rappel device that uses a clove hitch. Unfortunately, there are multiple combinations of loops that fail to make the secure clove hitch. Thus learn it well.
Here's a skill drill for you. Which image forms the clove hitch? Which two images would hold you?
Here are the answers. Number 4 forms the clove hitch. Number 5 forms a girth hitch. Thus 4 and 5 will hold you. The others are potential mistakes, so please be careful in your adventures.
Did you know that the clove hitch makes good one handed knot tying practice? Here's a sample of that: http://www.youtube.com/watch?v=K-4RMnULYIM