Watch this video for a complete step-by-step guide to the double half hitch (also known as the clove hitch knot).
Step 1: Using your leftmost cord as your "leading cord", pull it over the right cord. The right cord must now come up (& over) the leading cord. Here is an example of how it should look:
Step 2: Pull the cord through the loop & tighten. It should look like this:
Step 3: The cord must go up over the leading cord, then behind (under) the leading cord, and through the loop. It should look like this:
Step 4: Pull the strings tight & voila! You've made a double half hitch.