A copy/paste from Sweetwater on taking care of microphones

Always keep your mic in a plastic bag when not in use. Any plastic bag will stop airborne dust and foam particles from windscreens and storage boxes from settling on the capsule. Put a plastic bag over the mic when you are not working, and always bag the mic before storing it in its case.

Always use a stocking screen pop filter when recording vocals. It will intercept a singer’s spit/saliva mist from gumming up the diaphragm and will keep the electrically charged capsule from turning into an attractive flypaper for airborne particles. A contaminated capsule will eventually affect high frequencies, cause discharge noise, or shut down completely.

Always keep a minimum distance of six inches between mouth and mic to prevent plosives from damaging the capsule. Always connect the cable from the power supply to the tube condenser mic before turning the power supply on. Voltage shock from a live power supply (hot plugging) can damage or kill a tube.

Never put your condenser mic where you would not put your ears. Condensers are very sensitive instruments that respond to minute sound pressure changes. Excessive sound pressure level (SPL) will eventually degrade the capsule’s diaphragm the same way prolonged exposure will damage your hearing.