This is a tutorial that Scott and Malia did a couple of years ago. I've done posts on it before, but photo composition is a super important subject in real estate photography and this tutorial is worth watching again if you've already seen it.
The most important question you need to ask yourself with each photo is what is the story you want to tell with the photo in terms of features and layout and feel of the room. As Scott says "What is the photo about?"
Once you have that concept in mind of what the photo is about it can guide decisions about what to include and what to exclude. You also can recognize which visual elements of the photo distract from the story and which visual elements add to your story.
The three main concepts that Scott covers in this tutorial are:
Oh yeah, and you need to practice this stuff. Some people get these concepts faster than others, but we all need to practice to get good at it! Another good way to practice these concepts is to think and talk about your work and the work of others on the PFRE Flickr forum. Frequently others will see things you don't notice.