To check for mold in your house, look for visible signs of mold growth, such as discoloration on ceilings, walls, and around windows. Take note of any musty odors, which indicate the presence of mold. Check areas susceptible to the accumulation of moisture, such as bathrooms, basements, and underneath sinks. Use a flashlight to inspect hidden areas and consider using mold testing kits available at hardware stores. For a comprehensive inspection, hire professional mold inspectors who use advanced tools to detect hidden mold.