If you ever find yourself with the troublesome problem of having more foam than beer, there are a few tried and true methods to get more beer in that plastic cup. While techniques often vary, just a few simple moves get the job done time after time.
If the foam has already overcome the liquid beer, place your pinkie directly into the cup. The natural grease and acid off your skin actually eats away at the foam, leaving only the cold beer behind.
When filling your cup, tilt it at an angle and press the spout firmly against the inside rim. This will allow only a small amount of beer to stream into the cup, resulting in a smoother pour and less-to-no foam. The warm air reacting with the cold beer is the main culprit of the foam, so cut off its oxygen supply.
A cold glass mug will allow less of your beer to turn into foam by maintaining the beer's core temperature. Since it is cold inside the keg, the beer needs to stay cold to remain in liquid form. A warm plastic cup does not have the same insulation abilities as a glass mug does.
If all else fails, the foam will eventually subside on its own.