Another favorite request is "How do I make comic tones in Photoshop"...the reason I've stayed away from this one is that a) there's so many variables it's nearly impossible to say "here's how you do it" and have it work everytime. b) If you were really going to print you would be working at resolutions of 600dpi or higher which is quite the hit to your memory and processor.

This technique I'll show you is just for "mimic-manga" purposes. Don't actually use this for production....buy some tones from www.animegamersusa.com

Step 1: What a Drag

Grab your freshly made comic tone, and with the move tool selected, drag it onto your piece of artwork.
The tone will now be on it's own layer above the art. Change the tone layers blending mode to "Multiply" You will now be able to see through it.

Step 2: Erase or mask?

I prefer to use a layer mask when I'm removing the excess tone...but that's a whole seperate tutorial in itself.

The beginner way would be to just erase the stuff you dont need. Highlites can be added to the tone by painting white on a layer above the tone.