Dresses and things, too...

I'm having a bit of an issue trying to size dresses. What do I go by? How do I get my measurements, and how do they corelate with a dress? I've got everything else but a frigging dress... I want to get pass this side of fashion, so I can get to what I really want to be; modern, slick, chiché lines, bit loose, with touches of flair. I want to say business casual, but I'm more of leaning to my mother's fashion style. (Geezus Christ, I AM her...)

P.s. is it normal to take after our mothers? Seems like everything I do comes back full circle to her. -__-