Keeping an idea file is a great reference for everyone. A notebook filled with magazine tear-sheets, fabric snippets, paint swatches, photographs, and anything else that catches your minds eye. These files can be of great assistance when getting the creative juices flowing.
For me, due to my painting & art background, sketching what my fantasy for a project is usually where I start. I find that some of my clients have a difficult time visualizing my ideas....A sketch often shines a revealing light onto a prospective idea.Sketches are helpful in so many ways...For example, furniture placement and finding the holes where you can now create a furniture 'wish list.' I always do my best to incorporate pieces a client already possesses and show them how they will be transformed into the new space. Whether it be by re-upholstery or a change of paint & hardware....If it has great bones it's worth the effort and expense to transform it.
Of course, color is extremely important when sketching as well. I live and breathe color and therefore am always incorporating it into my drawings. It is such a vital part of my design process that it can help convince a color-reluctant client to take that leap of faith. Once they do....Watch out because color is powerful once it's unleashed!