The purpose of carnival games is to make money for the carnival itself or the game operator, who may be self-employed and not working on the carnival's payroll. The design of any games used in a public carnival (versus imitations for other events) incorporates a bias that favors the game operator. This may or may not involve pure cheating or a "scam" operation and the design of the game may involve an illusion about what "winning" really requires.
Overall, carnival games fall into two categories: games of skill and games of chance. For those games involving skill, you can learn the technique to make winning likely--even mastering that skill. With games of chance, however, even knowing the techniques involved in the game still leave winning a hit-or-miss risk. Some carnival games involve mostly skill but also have an element of chance.
Some carnival games that involve skill include: balloon dart throw, skee ball, shoot out the star, rope ladder and stand the bottle. The most common carnival game involving chance is that of the operator trying to guess the patron's age, weight or birth month; other carnival games involving chance involve any sort of random guessing such as what square hides a prize.
While skill-based carnival games favor the game operator, this typically involves a game design that presents some kind of illusion about the actual skill required to win. When you know the real technique necessary for winning, you can apply that skill to "beat" the carnival game. An interesting website that provides insight into beating carnival games, Blifaloo, identifies the correct technique for winning 10 common carnival games. Some involve a combination of skill and chance and the technique may not work as well with some of the others.
A fun way to use the principles of carnival games is to devise homemade games for such events as a child's birthday party or a fundraising event. When mimicking carnival games for this purpose, make the games easy to win to encourage fun for children or to reward patrons for contributing to the fundraising effort. Websites such as Coolest-kid-birthday-parties and Funattic give directions for devising such carnival-based party games as Feed the Lion, Penny Toss, Horse Race and Go to Jail.