I try to figure out the general stuff first and work my way to the specific. Like first off, is it going to be some kind of holiday oriented design, or is it going to be a "normal" house, or is it going to be something wacky? Those are the biggies. Holiday oriented I try to think up a theme and usually do a bunch of different areas that fit in with that. Here's a house I did with a giant tree for a contest that was "autumn" themed:
For a normal house I make lists of what I want in it, try to think of decoing things I have never done before (like this castle I'm currently working on, I try to incorporate something new into each area). Normal houses are probably the easiest because there is so much to draw on and you can do just about anything, and if something doesn't quite work out you can just do something else.
If you want to get crazy, you can make houses like a cute firehouse I saw someone do before, or make a park or some other kind of natural feature, make an illusion house like those giant towers or the piers that go off into the water...I did a giant cave on test center before, and just last week I got bored and decided to make some kind of modern art type plot that I would probably use as an open vendor house if I was going to keep it (I decided it was too boring after all):
Sadly I can't just drop the house and replace it to get rid of the gozas - the white ones are too valuable, hehe. But I can do that after I chop all the white ones and put them back in another house.
