Do not place magnets close to any source of heat, since you could permanently damage the magnetic characteristics.
Do not place magnets close to audio or video cassettes, recorders, televisions, speakers, magnetic credit cards, compasses, watches, etc. You could irreparably damage them.
Do not place magnets with the same polarity close to each other, the magnetic repulsion could damage the magnetic flow.
Do not place magnetic materials that are different from each other next to each other (e.g. Neodymium with Alnico). The magnetic direction and the values might face substantial mutations.
The use of permanent magnets is not particularly recommended for people with Pace-makers.
Store the magnets in a dry environment far away from sources of heat.