Some of the basic things a home owner can check:
1. Make sure there is no standing water in your crawl space or areas of excess moisture. (High humidity levels over 50-55% can cause mold growth, so any excess water is a problem.)
2. Ensure HVAC lines are connected well, this will prevent you from heating or cooling your crawl space and save you money.
3. Make sure guttering is doing the job intended, check for leaks and natural flow of the water and ensure the water is diverting away from the house so it does not come back into the crawl space.
4. While under your home check for moisture on pipes, this will allow you to catch any leaks before they get worse. If you are checking during the warmer months, remember that you may see some moisture on pipes due to humidity. A small amount is expected.
5. Always make sure your crawl space door secures well, in many cases a well cover will prevent excess water from getting into the crawl space.
6. look around your foundation for small cracks. Even small/minor foundation cracks allow water to leak into the crawl space and increase moisture and humidity levels under the home. In some cases creating the perfect environment for mildew and mold growth.