Ok, so this trick is to get the shot glass to stick to your palm when you press on it.
What you need is very simple, you need a shot of Sambuca, a lighter and a palm.
First you fill up the shot up with Sambuca, then you light it on fire, as the blue flame stays on top of the Sambuca, you place your hand on top of the whole shot, covering with whole shot cup with your palm. (letting no air in or out)
The shot will now stick to your palm, its a very simple trick.
The reason why it works is because as the heat from the fire cools down and the air temperature will create a strong vacuum which allows you to perform this simple trick.