One way of doing them (I'm sure someone else has an easier way), they can act the same was as a brush, and I actually only use 2 differnent ones.
Here are the basic two:
Scanlines:
square dots:
Scanlines-
Make a new file, 1 pixel wide, 2 pixels high make sure its a transparent background.
Zoom far in and fill either the top or bottom pixel black
[zoomed in 1600%]
Goto Edit > Define Pattern, and voila! You have a scanline pattern.
Dots:
Keeping that last piece open, just goto Image > Canvas Size
Set the change the width to 2 pixels, so its 2x2 and you should get this:
Now Edit > Define Pattern, and you have the dot pattern.
To use them, when working the layer you want the pattern on, just right click the layer, open Blending options, toward the bottom is Pattern Overlay.
Or you could always just use the pattern stamp tool:
Top: where the tool is
Bottom: where to change pattern(at the top of the screen once the pattern tool is chosen)
You really need to experiment around to get the results you desire!
