I have learned a lot from years of dolls housing, and I am sure you have too!
Please feel free to contribute your own tips - I'll post the best ones so everyone can see them.
Tip 1: Order and Organization
Both order and organization are crucial to dolls houses!You must decide if you will electrify the house, and if you will have running water (a rather neat feature!). Plan out the rooms, Plan the flooring and the walls, and the windows. Decide whether you will have wood, linoleum carpeting for each room. Paint, and or with trim, wallpaper, plaster, etc. And you can use paint on the ceiling or whatever else you want. That is the first step after electricity. Then decide what each room is, and furnish accordingly. Good luck!