For flooring. Hardwood, linoleum, vinyl, tile or stone are good choices.
For walls. Instead of wallpapering entire walls, consider papered borders or stenciling as decorative touches. Mold can thrive in wallpaper adhesives.
For closets and storage areas. Minimize clutter to decrease dust, a food source for mold and mites.
For bathrooms. Run the fan or open a window when showering, and let the bathroom ventilate for about an hour afterward.
For roofs and siding. Check regularly for leaks and fix them immediately. Avoid letting sprinklers spray the sides of your house. Keep your siding clean, removing mold and mildew; remove overhanging tree limbs so sunlight can help keep your home dry.
Keep gutters clean; if you don't have gutters, add them.
For crawl spaces. Insulate pipes and ductwork. After fixing any air and water leaks, ventilate the space; replace the crawl space door with a screen during spring and summer.
For outdoors. Make sure the ground slopes away from your house so water flows away and not under your structure.
For overall. Use your air conditioner and replace filters regularly. Also, make sure drainage pipes on your units are clean so they drain properly; extend condensation drains at least three feet past the foundation wall.