Selecting the scanning area: Always preview the document and select just the area to be scanned, instead of scanning the entire document. This will reduce the scanning time as well as the file size, especially when scanning at high resolutions.
Resist scanning at high resolutions: If you intend to scan your documents only to view them onscreen, scanning at a resolution between 100 and 150 dpi is enough, as monitors can only display 72 dots per inch (dpi). Scanning documents at higher resolutions will only result in a larger file size. If you are scanning a document for faxing or OCR-ing, 200 to 300 dpi is sufficient; for printing photos, 300 to 600 dpi is more than enough. For photo scanning, keep the setting at the maximum colour depth that your scanner supports.
Use the Descreen option: When you scan content from magazines or newspapers, you will notice a lot of moiré (converging and diverging lines) on the scanned image. The best way to reduce this pattern is to use the Descreen option in the scanner software. If your scanner software does not have a Descreen option, you can use an image editing software.
Image formats: Select an image format depending on where you will be using the image. If you will be using it for the Web or for animation, save it in JPEG or GIF—these compressed formats save a lot of hard disk space. On the other hand, if you are scanning the image for print, TIFF is the best format, as it compresses the image with hardly any loss in image quality.
Correct ghost images: A ghost image occurs when the scanner picks up images from the back of the page. This can usually be corrected by changing the brightness and contrast settings. Experiment to find the best settings for your scanner. Another simple way to correct this is to place a thick white paper over the document being scanned.
Adjust brightness, contrast and sharpness: Many a time, the scanned image turns out to be dull. This can be easily fixed through the TWAIN driver (if your scanner supports it) or using image editing software, where you can adjust the contrast and brightness levels.