Scanning your own images will save you a scanning charge. However, your scan must be of good quality or we will not be able to work on your image.
You want to use a quality flatbed scanner that will allow you to scan the image with its physical size 100% @ 300 dpi. View the image closely to make certain there aren't any scan lines.
If you do not have a quality scanner you can take your images to Kinkos or another like photocopy store and have them scan it at 100% of the physcal size at 300 DPI. That should be sufficient.
Scanned images should be saved in JPG (high quality) or TIFF format.