I close the lid!
*is hit with bricks*
Ok ok the real secret to scanning cleanly is what type of media you scan with and what DPI you use. Most scanning software will come with these (and other) options for you to use, and it depends on what you’re scanning that determines how good a result you get.
For colored stuff, I usually have it set to ‘color photo’, and I scan everything at a minimum of 300DPI. All the layout people in the audience will know that 300DPI is the lowest resolution allowed for printing, and scanning at 300DPI is a good way to make sure you get a nice, big, clean scan. If I’m scanning something that will be printed though, I usually bump it up to 500 or 600 and then shrink it back down to 300 when I’m ready. Why?
Because when you shrink something down digitally, the program removes pixels from it and this has the effect of “smoothing” the picture out so it looks a bit more even. When a program shrinks an image, it’s removing pixels from it and little details like small scratches and dots and things like that get reduced.
tl;dr: Scan big, then shrink it down. Hope that helps!