Here is a good way to get free beer in the US (If you can fill in a Weissbier properly, that is):
Go into a bar which prides itself on its excellent beer selection - this will be easy, lots of bars in the US have quality beer from all around the world.
Order a Weissbier (Yes, I got Erdinger, Schneider and once even Hopf in US bars), look critically at the way he fills it into the original Weissbier-glass. If the bar doesn't have the original Weissbier-glass, tell them. Imn a month they'll have them.
Tell the barkeeper that the way he fills the beer in is not the proper way. Show him the trick one, with the bottleneck deep in the glass and the whole procedure (hard to describe in english). The barkeeper will now want to learn the proper way. Like every human being, he will fail the first two or three times, and the barkeeper will look like a dork with the Weissbier everywhere but in the glass.
By now other Americans will have noticed the spectacle and begin to move closer. Eventually the barkeeper will manage the trick and there will be loud hoorays by everyone. The whole gathered crew will order Weissbier ("but fill it in the proper way, like the young dude did") and you will get free drinks. Worked everytime for me, extremely useful skill.