Fade in on SAM, a tall, gangly individual in his early twenties. He wears glasses, and his slouched in front of a computer, typing. He seems to finish something, leans back in his chair and turns to address the camera.

SAM

Obviously, to demonstrate the various parts of scripts I have to actually SAY something at this point, so that's what I'm doing. This paragraph you're reading right now is a "dialogue" class paragraph.

(points at this action paragraph)

That paragraph which said "(points at this action paragraph)", however, is an "action" class paragraph. It's indented much further.

He sips some water from a glass on his desk, and then continues to perform other activities. By this method, he also demonstrates this, a regular, classless paragraph, which has margins separating it from sections of dialogue and is much wider than the others.

SAM (CONT'D)

Finally there's the "name" class paragraph, indented the most, which just has a margin at the top, not the bottom, separating the dialogue it heads up from whatever came before it. The bit where it says "SAM (CONT'D)" is an example of this. View the source of this page to see the actual length measurements behind all these indentations - they are too tiresome to rehearse here. Remember, of course, to use the Courier font (failing that, any fixed width font) and 12pt font size.