So there are many ways of making a repeat pattern and here I'll list a few with a little help from some friends (strangers on the internet)
The Define Pattern is a very simple way of creating a repeat pattern (tutorial coming soon), however it does leave rather a grid like, regimented pattern. Great if that is what you are after. If however you want it a bit more organic looking I suggest you follow the tiling method.
This first tutorial from Mel's Brushes explains the mechanics, how the tiling process actually works. The Offset Filter does the tiling automatically for you but it helps if you have an understanding of what and how it is being done.
Tiling - Manually (superb results!)
Tiling with Offset Filter
Experiment with different tile sizes or area selection, here are two versions I did. What effect do these variances have on your pattern?
|Larger Tile 600x600|
|Smaller Tile 125x125|
I would suggest you try all of the methods and compare them. What worked best for you in terms of process and results.