I shoot "for sale" homes for a real estate company for them to post. I have my camera set on program (Canon 60D) and not too concern about professional quality, but it wouldn't hurt if I can achieve it. Generally, I shoot about 150 photos per home, depending on size. I'm still uncertain how to set the ISO to achieve a proper balance of lighting. Outside photos are usually OK but I have noticed some darker photos on occasion. Inside photos are the problem. Some rooms may be darker than others and if I use flash, I occasionally get white wash and if I don't use flash, the shutter speed is slow enough where my movement will cause blur. Basically, many photos are far from professional quality, but good enough to post.
How do I achieve the right balance and closer to pro quality?