How should you test for mold?

ERMI test. Mold toxicity is a surprisingly common yet often hidden factor in chronic health problems. While mold cultures have often been used in the past, experts in the field now feel the best test is the ermi (environmental relative moldiness index) which analyzes dna from mold spores found in dust. See http://www.Survivingmold.Com/docs/diagnosis/ermi/articles/ermi_v26_p32_filtrationnews_2007.Pdf.
Depends on surface. The primary issue with mold is the production of mold toxins. Air sampling can be done in different rooms and compared to ambient air samples. Carpet samples can be snipped and tested. Scrapings can be taken from flooring, walls, air vents, and counters.