Preservation activities aim to minimise the physical and chemical deterioration of records and other artefacts, and to prevent the loss of information content (this is also known as passsive conservation). Active conservation involves remedial treatment, preserving records or other artefacts in their original format, and should be undertaken by qualified professionals.   

To maximise the life of archival records:

• Handle carefully
• Store in appropriate containers
• Avoid exposure to extreme temperature and relative humidity (high temperatures accelerate the decay processes, cooler temperatures slow them down; RH levels above 65%  encourage the growth of mould and fungi)
• Avoid exposure to fluctuations of temperature and relative humidity (these weaken the fabric of the document and are particularly damaging to multi-layered records like photographs)
• Avoid exposure to light
• Avoid exposure to dust and other pollutants
• Avoid amateur repairs using sticky tape, etc.

Some useful links on preservation and conservation:

Conservation/Preservation Information for the General Public Conservation OnLine (US)
Collections Care The American Institute for Conservation
Caring for Your Family Archives The National Archives (GB)
Guidelines for dealing with water damaged recordsThe National Archives (GB)
NF-ISO-11799 Information et documentation : prescriptions pour le stockage des documents d'archives et de bibliothèques 
Outils et ressources en conservation – Gouvernement du Canada
Conservation OnLine (US)
The National Archives (GB)
The Institute of Conservation (GB)
TAPE Training for Audiovisual Preservation in Europe 
Memoriav – Preserving the audiovisual heritage (CH)