Cleaning up scanned line drawings

any tips on how to get them clean and crisp? black ink drawings is what im scannin in, ive figured this much out; scan it in at a high resolution (i scaned in at 600dpi), scan it in grayscale, mess with the levels. the overall goal is to scan in a line drawing and color it. im trying to get the lines to be a uniform solid black. ionno if this is something i should try to get when im actually drawing it or something that is best left to PS. it looks pretty good on paper but when i got it in PS the lines are not as solid as i thought. thanks for the help.

Try this very old tip by Kaï Krause, one of the first Photoshop gurus: http://www.gurusnetwork.com/kpt/tip/4/