Keep in mind that you may need a higher resolution scan to satisfy the two-times rule when you crop a photo. Avoid JPEG compression if you are going to use scans in print media, although the higher quality JPEG settings often work okay. Do not use GIF files in print media. These are 72 DPI and unless you reduce their size significantly in your document, they will not satisfy the two-times rule. In print media, it is important to make sure that the darkest areas of a grayscale scan are not too dark and the lightest areas are not too light.
Many flatbed scanners tend to scan dark.
In the Levels window note the input levels histogram. There are three sliders below it. The middle slider will allow you to lighten or darken the whole image as you see fit. Also, note the output levels slider at the bottom of the levels window. Likewise for the lightest area of the scan.