When I started I just went for it. Started drawing stuff that looked like crap, but I kept going and going and drawing more stuff. Eventually I went back and revisited some stuff and revised it and just kept drawing. The more you draw, the more you get a "feel" for what should look better and you learn to subconsciously do little things that make your piece better like combine clusters and add in small bits of AA around certain areas of high contrast of just jagged intersections of color. But yea, just start drawing whatever would be my suggestion.