I often say, 'Draw dumb.' (At least in the beginnings of a piece.) And what I mean by that is to turn off the part of your brain that thinks about detail, in order to leave your mind open to bold graphic choices and the all important 'flow' of a composition. It is the forest vs. the tree right? If I obsess details too soon, I lose sight of the entire painting, and it winds up looking like separate elements bashed together on one surface.
As soon as I start thinking about detail and hitting the reference hard, that is when things will start stiffening up. It is the nature of reality intruding on imagination. And in my work, the final result is (hopefully) a solid compromise between the two. That isn't to say I am not glancing at a variety of ref here and there in the beginning, but no more than a glimpse. I want to be consumed with what is happening in my comp and not what is happening in the corner of my eye.
One way I do this is by NOT starting with line when conceptualizing a piece. Instead, I start with shape (Which I often add some chicken scratch too). My chief tools for this are the Photoshop lasso tool, and a wonderful, though often forgotten, little program called Alchemy. (Which, by the way, is FREE!)
What follows are my original shape-comps and the final pieces. In the early stages I am concerned with flow, attitude, composition and value more than how well a hand is drawn or how much detail a costume has. We can ALWAYS refine. It is much harder to get back to the essence of a thing once it is frosted, has lit candles, and everyone is standing around singing Happy Birthday.
Here is a slide show of me building one of these shape-comps in photoshop, using nothing but the lasso tool, fill, gradients, brightness/contrast, and the all important Transform.
And here I build up a face in Alchemy to give an idea of how I use the program. I usually have my 'Create' tool set to 'Shapes'. And as I get into it, I switch on 'Gradient' under the 'Affects' drop down. So essentially it is like drawing with a lasso tool that auto fills with value and gradients. (And I use the 'Transparency' slider to adjust opacity, which lets me build up.) It is the speed with which I can create, and the lack of an un-do (by design) that attracts me to the program. Forces you to commit and make your marks count.