Creating tutorials?

[sonny_c]

This may sound silly but how do you create a tutorial like the ones found on good-tutorial.com?

I'm trying to make a step-by-step tutorial on my poster designs. Is it a word document, a pdf file, or something else? How do they capture just the image of their photoshop screen and not the entire desktop? Any other advise?

Any help would be greatly appreciated,
-Sonny