As a general rule, scan an image at twice the resolution of the screen it will be printed with. More dots per inch than double the screen resolution doesn't increase the quality, but it will increase the file size. This rule of thumb assumes a photo will be printed at 100 percent size. Use a larger dpi if the image is going to be enlarged and a smaller dpi if it will be reduced. Avoid compressing your scanned images unless absolutely necessary because of storage and transport considerations.
Compression can degrade the image and add more time to processing.
Digital prepress involves a great many topics and details too numerous to exhaustively cover. We recommend that you contact our prepress department for more information about your specific needs.