Beer and Food
Once you have a beer bong (basically just a funnel and a tube), you raise the funnel above your head.The farther above your head the better. The drinker must take the tube and bend the end of the tube so that nothing can come out.This will kink the tube much like kinking a water hose.The harder you hold it, the less likely the liquid will come out. Many people will stop the end with their thumb.
Filling It Up
A second person fills up the funnel. Depending on how much you've had, you could do this yourself. The beer must be poured in very slowly to decrease the amount of foam. If there is a lot of foam, either put a finger in it or wait. The salt on your finger will dissipate the foam.
There is some debate about this part. If you have kinked the tube, stated above, then put your thumb over the hole and un-kink it. Quickly put the tube in your mouth, and move your thumb. The liquid will flow through the tube and into your mouth very quickly. Gravity will push the liquid so quickly, you can drink a beer or more in seconds. The higher the funnel, the faster gravity pushes the liquid into your mouth and stomach. The kinking method will increase this with a sudden forceful rush of beer, rather than the steady continuous flow of already having the tube in your mouth.