Hi!
Here's a little explanation. I hope it will help. First I draw the entire character on a single sheet of paper with lots of attention to the detail. Then I scan it, adjust brightness and contrast in Photoshop. I usually use the Auto Colour option too, to get rid of the greyish tint most scanners give to the drawings. Auto Colour makes them very dark brown, close to what they look on the paper. Then I clean up the drawing using the dodge tool (set on highlights mode and about 60 to 100 percent opacity). It's great for that, you can erase any traces of smudging or bring out light in small details. You could use also the burn tool for darkening some lines, but be careful because it burns them very easily. It should be set to a very low opacity, like 10-15. After that I paste the whole thing as a new layer on top of a texture, usually an old paper one.
Take Care
-Asya