Mold typically grows in well-saturated areas. Basements, bathrooms, kitchens, and garages are commonly invaded by black mold. If you suspect mold in your building, start looking in the rooms that hold the most water. Even if an area is not normally water-prone, a leak can lead to mold. Leaky water pipes are often culprits, but you can have other sources of water, too. If your air conditioner is not properly drained and insulated, it can leak water. This can result in black mold around the leak. Porous materials such as grout are often used to join two slabs or panels. For example, kitchen and bathroom tiles often have grout between them. If water frequently gets into the pores in the grout, black mold can grow there. Sealants can also be prone to growing black mold. Sealants are often used in high moisture areas (e.g. around your shower). Because of this, black mold can set up and grown on a sealant, such as calk. Black mold naturally grows on materials containing cellulose. These are plant based materials such as paper, cardboard, and wood. Keep a close eye on any paneling or file cabinets that get wet. Any wood, drywall, carpet, or cloth can easily grow black mold under moist conditions.

Summary:
Seek out naturally damp areas. Inspect any leaks. Look at joints. Check any seals. Watch materials high in cellulose.