SCANNING TIPS

IMAGE RESOLUTION
If you were to use an image scaled down to 50% of original size, this would double the image's resolution. Scaling a particular image to 33% of the scan triples the resolution, etc. A final resolution of 1.5 times the LPI works well in most cases. LPI stands for lines per inch, and for offset printing the LPI is usually 133 or 150. Final scan resolution means that you've calculated the change in spatial resolution when you size your original scan, so the formula is:
DPI = LPI x % increase or decrease of original x 1.5 

CROPPING
Crop the image in an application like PhotoShop as close as possible. Avoid using your page layout program's ability to crop a scan, this feature merely masks an area and does not decrease the data.

SHARPEN
Sharpening the image in a retouching program gives a better looking result. Make the on-screen image just a little sharper than you think is needed - it softens a bit in production. Your scanner reads the grayscale data as linearly balanced, meaning that the transitions between grey areas tend to be minimized. Sharpening algorithms in a retouching program like PhotoShop can adjust for this. Always run your program's Sharpen routine on a scanned photo

DESCREENING
If you frequently scan printed matter that is screened at 133 LPI or above, you probably see a moire pattern when you view the file in a photo manipulation program or attempt to print the picture. Try scanning at 718 dpi (with descreening on if your scanner has this function), apply PhotoShop's Noise: Median filter with a 2 pixel radius and reduce the resolution to 225 or 300dpi.
Then apply an unsharp mask with the settings at 50 percent, 3 pixels and a threshold of 5. You may have to play with these settings but you should get something acceptable.
 
LINE ART SCANNING (Signatures)
Line Art scanning is considered 1-bit scanning, that is the computer sees the image as either black or white. Line Art should be scanned at as high a resolution as the final output device to eliminate the jaggie effect.

When a line art image is required from art that is not black and white (for instance a signature drawn in blue ink), you may accomplish this by scanning the object in as grey scale at 1200 dpi, then use contrast and brightness in an image editing program until you get a 100% black and white image. Then convert the result to a bitmap image. If you will then be using it with a spot color in a page layout program, you should save it as a tiff.