Creating Specular and Diffuse maps

I need specular and diffuse maps in order to improve the quality of my game. I have Photoshop CS3 and Gimp. I didn’t find anything useful by googling for a tutorial, so I decided to ask here.
Please tell me how to make specular and/or diffuse maps in Photoshop or Gimp and how to make them look good in Blender.

A google search for create specular maps led me to this link
Also many texture tutorials here

As I previosly said, googling didn’t help me. I need step-by-step instructions on how to create diffuse and specular maps from images, because I am not a pro in Photoshop.

I take it then that you didn’t watch any of the tutorials then.