How? I think having 1 in my work wardrobe would be a good idea. Generally I wear blazers or long sleeved tops/jumpers but I've got a couple of smart shift shape dresses plus a couple of more relaxed jersey ones where having one to put over the top would be handy.
I always get them wrong. Am short curvy and short waisted. Long ones swamp, belted ones make me look like a barrel and smart fitted ones are always a bit droopy and hide my waist.
Tips? Probably size 12.