1. Keep the pictures not in plastic albums, but in ones made out of paper (or paper envelopes). There's some in the stores, but the best ones are the ones made specifically for this purpose, such as the ones at the Photographic Heritage Center, acid-free. The pictures should be glued to the album with a neutral adhesive, and be separated by translucent paper.
2. The photos must be kept at a clean, dry and dark place, with a moderate temperature (not hotter than 18 degrees Celsius). Humidity must not raise above 45 per cent. Good places for this are drawers, but not in closets nor storage, since those tend to get dirty.
3. Do not keep the photos near toxic substances such as glass cleaner solutions or shoe shine.
4. Protect them from insects and mice.
5. The less the touching, the better.
6. Avoid exposing the original copy. It's better to make a digital copy.
7. Never use things such as scotch tape. You have to be careful will all types of glue.