Often, and I’ve been guilty of this too, users will just leave the settings as default and scan the image, regardless of source or colour. Having carried out significant scanning of late, the result improvement achieved by taking the additional time to set the scan software correctly is well worth it.
Using Canon MP Navigator as an example, an application that ships with Canon printers and scanners, I have the choice of a number of formats (see image).
By taking time to select the format of my source image or document, the results are significantly improved from a simple default scan.
Note too the resolution of the scan.
If you intend to print out a good quality image then use a minimum of 300 dpi. If it is a web-based image then 72 dpi or above is fine.
You can often up the scan level to a higher setting (600/1200 dpi) but this takes a lot longer to scan the source image, creates a larger scan file and is often unnecessary.