(Quick Mask in a Quick few steps)

         Open your picture in photoshop. Select the whole picture and hit ctrl C that's the same as making a copy. Then create a new layer, change the name to "line art".. Then take the paint bucket while still on the "line art" layer and fill that blank layer with black paint. Then enter the quick mask. Paste the picture down while you are in quick mask. Once it shows up all the black lines should look red on a black background.. Then EXIT quick mask.. Got up to "edit" on your menu and hit clear.. and Tada! its, its own line art

This is making a transparent copy of your drawing that is just the outline so as you color in layers under it, you can still see your drawing.