My solution - I create full size newspaper templates of the furniture I would like to place in the room and move it around the space. It makes it much easier to see what works and what doesn't. For example, once I laid out the desk and futon I could see that it might be difficult to walk around the right side of the desk. I could see one of us bumping into it a lot. That is how I figured out that the new side tables should be less than 18" leaving at least 2' of space to navigate in and out of the desk.
This is such a simple exercise but it will save you the aggravation of carting home a new piece of furniture only to realize that it won't actually work in your space. I definitely recommend you give it try next time you are rearranging a room in your home.