Winging it works fine for me, but recently I've started to evaluate my workflow regarding setting up the optimal scene.  The approach begins with either characters or props, work out the exact parameters how the scene will translate with the models inserted.  Will it be more landscape or portraiture?  Will I need hires textures?  Lores textures?  Do I need to create normal maps to reduce the render load?  Do I need a zillion shaders for the model standing at a distance?

Those decisions will govern how extensive the scene load will be in terms of disk space and render.  Anything to reduce that load will make it easier to compose the scene. 

Next, tackle the lighting.  This is easy to overlook, but very essential when you want the render to look right.  Realism is another thing, but using lights correctly will make or break the scene.  Develop character poses and set creation in separate files, then merge the two when you are satisfied with the final results.  Nothing is more frustration than developing the characters in a fully furnished set and having nothing work out the way you chose. 

Concentrate on easy aspect separately, and if you need to commit the ideas to paper or storyboard, then do so.  Taking a different approach will refresh the idea from another viewpoint.