When I launch a commissioned work, there are so many possibilities!  So I get my clients involved at the very first step: the composition of the work.  Invariably, using a sketch in black and white, or rough color, to start the conversation with the client enables the client's mental images to become more specific.  Maybe the client wants a "big sky" painting, but her spouse wants something that includes clouds, and the family's image should be recognizable, but not too big in the context of the vastness of the overall scene.  Sketching and sharing, via email, allows dialogue about what feels right to the people who will look at the painting for many years to come.  It builds excitement for them and for me!