Basic Dirty Texture

1) Make a 400x400 document. You can edit>fill the background layer to any colour you want, I suggest a moderately dark gray

2) Go to Filter > Render > Difference Clouds and something like below will form.

3) First Ctrl+Click on the layer you just created. Now Create a New Channel by Clicking on the "CHANNELS" tab, and clicking the create new layer button.

4) Repeat the Filter>Render>Difference Clouds, that was done in step2. the click back on your main layer.

5) Now Go Back to the first Layer you created, and go to Filter>Render>Lighting Effects and enter these settings.

*NOTE* that the Alpha one Was chosen.

6) Still on main layer, go to image>adject>hue&saturataon and choose a desired colour, I chose a yellowy colour, and here is what I came up with!

Enjoy! Tell your Friends!