>>472904essentially you need a good source image to scan... newspapers are the worst, super high quality magazine (i.e. National Geographic) are much much better source... or an actual photograph can be a good clean source.
of course, you don't often get the choose where your source is coming from...
get a scanner (and scanning application) that has built in "descreening" function - this helps a lot. after that you can play with filters to try to reduce that moire pattern effect you get from scanning an image that was printed using the 4 color print process (i.e. pretty much everything; magazines, books, newspapers etc etc)
beyond that you can try to scan you image HUGE then reduce the size later - this also does a pretty good job of reducing the moire effect... but to scan HUGE you might need a good amount of RAM in you 'puter to process the data from the scanner...
now, if you have access to a more professional DRUM scanner then you are all set! they produce images much much better then any flat bed "home" scanner...