Tongue tricks generally require a combination of flexibility and practice, usually in front of a mirror. Tongue tricks are demonstrations of an ability to twist one's tongue into unusual shapes or to use one's tongue to do things that tongues do not normally do.
The most common tongue trick is the ability to roll the tongue into a tube-like shape. This is done by rolling the outer edges of the tongue up and around so that the right and left edges touch each other at the top. Only 65 to 81 percent of the population is capable of performing this simple trick; females are more likely to be able to achieve it than males. However, because this is a learned behavior rather a simple genetic trait, it cannot be used to illustrate inherited traits with any accuracy.
Another trick is the ability to tie a cherry stem in a knot in one's mouth. This trick is often performed in bars as a bet. The stem of a maraschino cherry is placed inside the mouth. The trick is performed by clamping one end of the stem between the front teeth with the mouth closed so that spectators are unable to see how the trick is done. The tongue loops the stem around and then pushes the other end through the loop. When the stem is removed from the mouth, the teeth catch the trailing end again and pull the knot tight as the stem is removed.