Recently, I was asked to do a little synopsis of how I import my drawings into Flash. So here goes. Basically, I start with a pile of inked drawings. These are scanned on a regular flatbed scanner with a pegbar attached so that all the drawings register. These are all saved as .tif files.
Next, I batch import all of the tif's into a program called Adobe Streamline. This program is somewhat old and I don't even think Adobe makes it anymore. Mine is only usable in OS 9 (Mac); but it's a great program for tracing bitmaps and turning them into vector files. I highly recommend avoiding the "trace bitmap" function in Flash, it really screws up the line quality. Streamline is very faithful in it's tracing and I highly recommend it.
Here's an example of the before and after:
On the left is the scanned drawing. On the right is the vector image.
Hope this helps some!