Very, very, very important:
No high pressure air blast. I've seen them at 50K miles untouched and still OK. One blast with compressed air=ruined.
Let it dry completely after cleaning and before oiling. They will buckle and the material will get sucked into the motor, or just make it run super rich and foul plugs.
Very, very LIGHT on the oil. A super light mist is all you need, more oil won't filter better, it will just make it run rich and eff up your sensors (especially true in a car with a mass air flow sensor).
I don't want to start an air filter preference war but I went back to "dry" filters a long time ago.