I usually start with a nice shape for the great room. Interesting, but not wild. And I usually have am attached hallway to the bedrooms. Attached to the foyer and great room is a half-bath, when the dining room is separate, make it small, because a dining room in the sims doesn't take up as much room as it would in real life. I usually enjoy a large kitchen with an island and a bar-stool, then a small table some what sectored off of the rest of the room for an eating nook. The great room will have skill objects, but the bedrooms are what really express the sim's personal style. I like to do my best architectural work in the bathroom, because it can either be a perfect architectural work of art, or a toilet and shower dumped in a shoebox.
(That was just a bunch of architectural blabber for you, sorry about that)