The video below does a good job of showing you how to tie a standard clinch knot. To make it easier to see how the knot is tied, the video uses a carabiner (instead of a fish hook) and rope (instead of fishing line). But you should have no problem tying the clinch knot on your own fishing hook after watching this video.
While the video above shows you how to tie a standard clinch knot, this knot has been improved upon. The "improved clinch knot" is very similar and only contains one extra step at the end. The advantage of the improved clinch knot is extra strength. The video below shows you how to tie the improved clinch knot.