The best results can be had with an IT8 target and then an ICC scanner profile created through a calibration software tool like those offered by Monaco or Gretag-Macbeth
I'd suggest you get a print target and a transparency target and setup at least two different ICC profiles. I'd also recommend you use the Adobe RGB gamut as your working space. I have an ICC profile for colour transparencies, SCALA transparencies, colour negatives, B&W negatives, colour prints and B&W prints. Each profile tweaks something just a bit to ensure the proper rendition of the media I am scanning.