Where Does All the Dust Come From?

Today one of my clients mentioned have recurring dust issues in her home.  I have had those issues too and it takes some detective work to get it under control. It's a constant battle that I am beginning to conquer.  

Before I replaced my leaky vacuum cleaner, the day after I dusted the dust had returned.  Even now I find that whenever I've been moving things around, bringing in new items (like Christmas decorations from the garage), or doing laundry (using the dryer and folding clothes), that more dust shows up on my glass tables, etc. We don't open our windows very often because we do live near a high traffic area but