I vary. I like to add detail, as anyone who read my stuff will note, but I typically avoid doing it for people, reserving it for background scenery and animals/creatures. I don't like the stories that start out, well I guess I should describe him or me and then go on to give height, weight, hair and eye color almost as stats but it won't preclude me from reading the story, though it does turn me off it a bit and I might take points away if I was ranking it. I like to add detail as the story goes along if I can. If it's a short story then I admit, that's a lot harder. Besides, over-detailing prevents the reader from making their own mental pictures.