Judeau, 
I am in the process of selling off massive chunks of my video game collection.
Before I sell, I am scanning many instruction manuals that I see are either missing or have terrible existing scans online.
I am scanning at 300 DPI. This is overkill but will preserve all of the detail if they ever need to be blown up in size.
I am saving them as PNG and will then save everything as a PDF.
Does anyone have any tips or suggestions? All input is welcome.