Open all windows wide for an hour each morning or if the weather is bad, open them just a crack and leave them open for as long as possible.
Put cat litter trays inside those igloo things to contain smell and if the litter goes into the rubbish, use scented nappy bags to decant it into.
Wash floors frequently. I use Method almond or Johnson's soapy cleaner which has a mild orange smell. Avoid floor wipes. They have a smell that quickly sours and smells dirty.
Instead of harsh chemical sprays for cleaning surfaces use something like Method lavender or rhubarb, or just hot water with your favourite scent of washing up liquid.
Put a ball of cotton wool with essential oil on it into the vacuum cleaner - try lavender, geranium, lemon or pine. You can also rub a little bit of fabric conditioner onto the radiators in cold weather. When they heat up they give off a lovely fresh laundry smell.
Make fresh coffee, bake bread or toast waffles. Put your perfume on in the hallway not the bathroom or bedroom so it slightly scents the house, (if you wear any.)