This is a texture I made for a modification for the game Call of Duty I'm making with a group of people. It wasn't difficult to make. Just first get the basis, which in this case was a sort of brownish and blurry (motion blur) texture with black stripes which have a distance of 128 pixels. Then just keep on adding quality over and over again. Add knotholes, add dark spots and slightly differently colored parts (the wood is weathered) and most importantly the fibre of the wood. I experimented heavily with the Mezzotint (long and medium stripes) filter, and resizing it. Then, in the end, just use Photoshop's Offset filter and move the texture around so you can see the grid effect. This is when you finalize the texture by making sure it loops perfectly. To make the planks look a little more 3d, I added an Outer Bevel effect to the black stripes with Color Dodge and Multiply as blend modes. Very little opacity, and a Texture Bevel effect at small amount of depth. In the end, just change the colors around until you get something wood-like.
This texture is sized 1024x1024.