Repeating Pattern Tutorial

Make a new image 600 x 600 in size

Draw your design in the centre of the image, without letting anything touch the edges.

Go to Filter > Other > Offset

Use the values above. If your original image was a different size, simply enter a value of half its width and height. Et voila, a perfectly quartered image

Now continue filling in the centre of the image with more of your design. When its done, turn it into a pattern by going to Edit > Define Pattern. Here is the end result