The scanning process itself is crazy fast and you'll end up with a perfect scan - no need to adjust levels or remove smudges, scratches and noise because of the texture of the paper.
And the best part, at least for me, is that the scan itself will be cut out from the background so you don't have to spend time removing it and can move straight on to colouring or whatever you'd want to do.
You can only use this procedure with white or, at least light, paper with sketches drawn using ink, felt tip pens, markers and the like.
It won't work as well when you've used a lead pencil or something else that leaves smudges and/or has a faint edge.
You need a scanner (duh) and Photoshop or similar graphics software like Gimp.
I used a semi-professional Agfa scanner but even the cheap ones will work, the only important thing is that it needs to scan at twice the resolution you want to end up with.
So if you want your finished artwork to be in 300dpi it has to be able to scan in 600dpi, this shouldn't be a problem since most modern scanners can do more than twice that.
In step 4 you'll find a quick rundown for people who know their way around Photoshop as well as some final notes and examples of the difference between this scanning method and the "regular" one.
Also, please note that it's important that you do all the steps in the exact same order I describe or you won't get the same results.
Step 1: Scan your drawing
I use an Agfa scanner with the included Scanwise application so, from Photoshop, I just choose Import->Scanwise from the File menu.
Unless it's done automatic, press Preview and select the parts you want to scan.
Set the original image type to Line Art or, on some scanners, Bitmap.
The other choices should be something like Colour and Grayscale.
As I said in the introduction you need to scan at exactly twice the resolution you need so, since I want my finished example to be 300dpi, I'm setting it to 600dpi.
See second attached screenshot.
This should be very quick since it only scans black and whites, no grayscale or colour information.
Once it's done, quit your scanning application and go into Photoshop.