P.G.
I always used the rule of thumb on whether not you can tell you're pregnant from behind. If you are all stomach it's a boy, it's a girl you're all hips!
When my girlfriends and I were in highschool we did a baby predictor with a pencil stub hung by a needle and thread stuck in the eraser. It would predict how many children you would have and what sex. It was pretty close on most of us!