Start with a layout and a scaled space plan.  Ask yourself these important questions:

1. How many people do I need to seat in a space?
2. Where are the sofas going to go?

From there, then you can fold the color and design elements into the room.  Layer one thing at a time, like mixing the batter of a cake.  The walls, the rugs, the draperies and the colors will come to you later in the process.