Avoid thick wall-to-wall carpeting

Use tile, wood, linoleum or if you must have carpet, use less dense "Berber" carpets. Wall-to-wall carpet is like a filter you never replace — even if you vacuum, it holds dust, dirt and other tracked-in toxics and allergens.

Park your car outside

Seal attached garage/house walls airtight and install an exhaust fan in garage. Better yet, park your car outside. Cars are loaded with toxins which off-gas — avoid bringing them into the house!

Avoid toxins

Avoid toxins (pesticides, solvent based paints, etc.) in your house. Store any potentially toxic materials in airtight boxes in an outdoor storage unit or in a detached garage. These toxins can over time migrate out of their containers and then move around inside the home.

Remove shoes in the house

Shoes track in all sorts of unhealthy things, including dirt, toxins and petroleum products.

Avoid urea formaldehyde

Avoid urea-formaldehyde containing products, especially particleboard. Urea formaldehyde is a frequently used building adhesive that can create respiratory issues and may cause cancer. If you have a lot of particleboard (cabinets, shelves, trim, etc) it should be sealed with a laminate or vapor barrier sealer. Also avoid furniture made with particleboard and fabric coated with 'stain guards'.

Use no, or very low, volatile organic compound paints,
sealers and cleaners

These materials off gas a lot of chemicals into the air, including volatile organic compounds (VOCs), which can cause significant respiratory and nervous system problems.

Keep the home clean with low dust and clutter levels

Damp dust, mop and vacuum weekly.

Fix moisture leaks immediately to avoid mold growth

Eliminate moisture problems around the house.

Ventilate your home

If your home has a whole house ventilation system (in homes built after the early 90s, on a timer), ensure it runs eight hours a day. On older homes which have been well sealed/weatherized, run your bath fans eight hours a day. Ensure the moisture level in your home does not exceed 60% (use an inexpensive hygrometer to check this).

Seal air leaks

Seal the air leaks between the crawl space and the house, and in the ducts in crawl space garage and attic - This also helps with energy efficiency.