When you are making out with a girl while you have a dip in your mouth. Then spit your wad of chew into her mouth. If she spits it back to you, she is a keeper.
My buddy had a big fat wad of Griz and was making out with this Upper chick with only three teeth at the bar. He thought is would be funny to give her a Upper Slushy. But she was a snow cow and didn't give it back.