I start on a room, usually a bedroom and decide how big I want it. I then do the walls and the floor of that room, and do a door. Based on my colour choices and the way I'm feeling at the time, I then select the furniture for that room. Then I go onto a different room and do that and so forth. After a while, I realise I don't like it and so exit and start again.
This time I start with the shell of the house, and think, I need a dining room, a lounge room, a bathroom, a kitchen, a study and a games room on this level. Then I realise I need steps to go to the next level for the bedrooms and extra bathrooms, and a big family type of room for toys and what not. Then I generally decide on what I want outside the house regarding landscaping. After all that, I put in the furniture I want. Often, I realise that this is boring me and I don't like it as well. So I start again.
When it comes to dynasties, I generally just build one or two walls up, with a toilet, shower and sleeping bag until my sim meets his/her rich partner and I build a simple house with a large room for kitchen/eating/study/entertainment/kids, a larger room for the future museum, a smaller room for the bedroom and an even smaller room for the starter bathroom. Then I put in what I consider the essentials as far as furniture goes and builds a fence in parts of the grounds for the future garden/fishing pond/etc. I like modifying the colours of furniture etc in game to have unusual combinations.
I also had a fridge that the game wouldn't allow me to sell. It was in my kitchen and had an odor in it. so I built a small basement away from the house and stuck it in there and got myself a new fridge, which got replaced very soon after for the Culinary Career Reward of the -1 Kelvin Fridge.