1. Don't put a vapor barrier or rigid insulation board on the ceiling of your crawl space (unless your home is on stilts).
2. Don't close vents without sealing the earth.
3. Don't seal the earth without closing the vents.
4. Never use a fan to blow outside air into your crawl space.
5. Don't install a liner or concrete without removing organic material such as wood, cardboard,insulation, etc. from the dirt floor first.
6. Don't depressurize that has compustion appliances (more than one pascal)
7. Don't run your Dryer vent into your crawl space.
8. Don't ignore the problem.