Here you're going to learn how to define and use patterns that are useful for adding that final touch to images that makes the difference between amateur and professional.
1. Make a new document with a transparent background. The size is up to you but I'm using 5x5.
2. Change your foreground color to some gray. I'm using #969696.
3. Draw some sort of pattern that you want to be tiled over the page. I'm using this 5px by 5px one:
4. Go to Edit > Define Pattern. Name it Box or something.
5. Now we're going to use the pattern on a different image. So open the image that you want to put the pattern on. I'm just going to use a blank image as an example.
6. Select the area that you want to fill with the pattern with the Polygonal Lasso Tool, like this:
7. Hit M to select the Rectangular Marquee tool.
8. Right click inside your selected area and choose fill. Under the category Use, select Pattern, and on Custom Pattern, select the one you just defined. Click Ok.
9. Photoshop fills your selected area with the pattern you defined. Try changing the opacity of the pattern layer to get a less-dramatic effect.
More Tutorials: 
