How Do I Know What I Think Until I See What I Say?

The dilemma a lot of writers have, including me, is how much character description to put into a story. Too much, and the reader's vision of a character in contradicted at every term. Too little, and you're not giving the reader enough to work with.* So what to do? 1. I feel like it's important for a reader to have a general idea what a character looks like. I try to sketch a general physical impression of a character--height, weight, body type. 2. I find that if I describe one character whose appearance is important, I can describe other characters in relation to her. Is character B taller or shorter than character A? Wider or slimmer? Darker, or more fair? 3. A description of a character's movements can give a reader an impression of the character just as well as a detailed description of physical traits. Is the character quick or slow? Graceful or awkward? Athletic or something that is the opposite of athletic? :) 4. Physical description should reveal