From WikiHow, instructions on How to Gleek
This caught my eye because it seems to me to be a rare "talent"; my big sis can do it at will, and I can do it most of the time and quite often involuntarily when I yawn. Maybe it runs in families, I dunno but when I've done it for people it's almost always impressed them. To be honest, they were my friends and, like me, are easily amused.
Gleeking is the act of stimulating the saliva glands underneath your tongue into spitting a concentrated jet of pure saliva. Usually, it happens naturally when you yawn. It takes practice and concentration to gleek on purpose but these steps will help you learn how, so you can add it to your arsenal of body tricks.
More at:
How to Gleek