To avoid blurry pictures when hand-holding your camera, set your shutter speed to 1/(2x[lens zoom]) or faster. For example, if lens is set to 50mm, shutter speed should be a least 1/100th of a second.
To capture the perfect interior photograph, whether it's for a real estate listing or for an architectural magazine, some sort of flash is necessary. While you will certainly hear people who prefer to use HDR...