I make a lot of patterns, and I've taken a few pattern related classes, and I always assume everyone knows how to do it. But I guess it's one of those things that kind of need explaining. So I pass on my wisdom to you. Patterns have a lot of applications, not just in textile design but in illustrations and websites as well.
I hope that this tut makes sense. I tried to keep it simple, but maybe that makes it harder to understand?