You know that room that everyone has in their house and never uses? Leave it out. Like that formal dining room that gets used only at Thanksgiving, Christmas and Easter (or whatever holidays you celebrate.) Don't bother. Save yourself the cost of 150 sq. feet or use it for a room that you will use regularly.

Do 9 ft. ceilings in the rooms you will spend a lot of time in. It will open things up alot and make the house look much roomier.