Sharpies are a good choice to use on photo paper because they will not damage a photo and they show up on the photo's surface. Once dry, a Sharpie will not rub off of a photo in typical cases. Many people like to use Sharpies to sign photos or to add fun designs. However, a Sharpie can smudge and ruin a signature or the photo. It is important to properly use a Sharpie on a photo so that this does not happen.
Place the photo on a flat surface if possible.
Write or draw on the photo applying normal pressure. It is not necessary to press down hard.
Allow the Sharpie on the photo to dry completely before touching or before placing anything on top of it. If you are in a hurry, you can wave the photo through the air a few times to aid in drying.
Use a metallic Sharpie for a classier look, but allow extra drying time.