You use a pin, needle, or wedding ring and attach it to a thread or strand of hair. Hold the dangling item over the belly. If the needle or wedding ring swings in a strong circular motion, you will be having a girl. If it moves in a to and fro motion like a pendulum, you will be having a boy. You can also try this over the wrist instead of the belly.
I did this one today, over belly and over wrist. Both of them swung strongly in a circular motion. I's say that means Girl
Girl- 8, boy- 4