Dude its actually just observation. I mean if the chick is wearing a leaopard skin shirt she'll probably have a matching bra. If her pants are really low cut and there's no g-string or other under garments protruding she'd probably going commando. I mean it seems like a trick or magic but its just observation. One key elements to mentalism is pure pyschology. Practice observing people. For small example if you see someone coming out of there house and you notice hairs on there clothing they probably have a cat or dog. Observe and Discover my friend.