Such is the art! This is one of those things where it is much easier said than done. I've come upon this issue before, and I don't expect to ever get on top of it myself.
The writer, Mary Gordon, did an excellent piece on the subject. She holds the would-be writer off on describing a character, urging her to first lay out the storyline, what is going to happen next and after that and so on until the end. Then at the end of the essay, she tells the writer to go back to the beginning and describe the character - so that one will have a better idea of what it is one wants to show. Gordon's essay is especially powerful in the reading. I wish I knew how to direct you to it, if you were ineterested, but it's now just a vague memory for me.