I evolved this way, though I'm far from gifted. Starting out, anything I made was driven by whatever sounds I was noodling with. Now, I almost start on the piano, compose the outline, and then pick the sounds that I think fit it.

The first approach has a sense of creative wonder to it, where your being guided by an outsider. As much fun as that is, it is very limiting and I suspect most people abandon that approach as their skill improves.