Do use pure wheat starch adhesives, which can be bought ready-made and are best for archival material.
Don't use sticky tapes, staples (or metal clips of any sort) or rubber bands for repair or storage. The tape will become brittle and leave a deposit of sticky matter, the metal clips or staples will rust, and any rubber band will deteriorate and may produce a sulphur deposit.
Do seek expert advice about repair or storage issues if in doubt.
Don't try to clean any documents yourself. Especially don't use bread as a cleaner because it will leave crumbs and oil which will attract insects.
Do store in lignin-free, acid-free and for any photographs, sulphur-free envelopes or boxes. As an economy measure clean, non-abrasive, 100% cotton material can be used.
Don't store any documents or photographs in plastic bags because the plastic will eventually deteriorate and the documents may become stuck to the bag with the image or text off-setting onto the plastic.
Do keep memorabilia safely and snugly wrapped up in the dark so the ink doesn't fade in the ultra violet light. Use good quality copies if you want to display any items.
Don't leave documents and photographs in damp conditions, in the sunlight or by any source of heat as they will become yellow and brittle.
Do buy the best possible materials you can. These are usually obtainable from a good quality art supplies shop. Store them correctly for their maximum lifespan.