Uh oh, the fun's over and now the technical stuff begins. How to make a clean, clear image you can color on. I tend to scan an image at 300 pixel resolution so we can color the high-res version and shrink it down later. You'll need to adjust the image to get rid of the noise that tends to show up with scanning and get rid of those light eraser marks that always get left behind.
It's important to zoom in on the image to %100 so you can see how your image is clearing up. Once you've done that, open up the brightness/contrast (yes, I know about levels and curves, no emails please ;)) dialog box and change the settings till it looks pretty black and white. 21 and 33 seemed about right to me but every drawing is different.