Step 5 = Insist on no outdoor shoes in the house.
Keep pavement muck and germs (i.e. dog pooh, urine, mud, takeaway remnants...) out of your home by insisting that everyone who enters does so without their shoes.
This is especially important for homes with young children, well any age children really, as they naturally play on the floor.
Keep a wooden crate / basket in your entrance hall so you don't actually have to say to your guests, "Please take off your (germ-laden) shoes!" Just indicate the crate / wicker basket / plastic trug and say, "That's where outdoor shoes go."
It helps to have slipper socks or even spare slippers to offer your visitors, especially if (like us) you have bare, drafty floorboards.
I finally found some washable slippers at M&S (ideal if you are offering slippers to guests who are barefoot-shoe / sandal-wearers in the summer months) - no one wants to come to your home and catch a nail infection or foot fungus from unwashed shared slippers.
The washable slippers have survived at least 6 months fortnightly machine washing at 40 C (with Napisan of course...) in our house. After 6 months the sole starts to disintegrate... But they are reasonably priced, so I got two pairs (one to wash and one to wear in the meantime). If the M&S slippers are out of stock, you could 'invest' in some beautiful Giesswein 'Lauenau' felted-wool slippers for £45, which are machine washable. *UPDATE* if you have these gorgeous slippers then DON'T wash them at 30 C as instructed by the manufacturer, as they shrink and the rubber sole partially melts and goes 'tacky' in places. This was despite me zipping them into a net bag during washing and including 2 hand towels in the drum to buffer them. Luckily the customer after-care is excellent - phew! I will wash my replacement pair at 20 C from now on, with Dettol Antibacterial Laundry Sanitiser added to the wash, which works even at 15 C.
I wear the (beautiful) washable slippers and (any barefoot) guests in our house make-do with slipper socks.