What street tricks must be guarded against?

A few years ago, when I was opening a clothing store, I met a group of swindlers. They guessed corn and beans and gave me double money, such as betting 100 yuan to win 200 yuan. Wrong guess, lose 100, and then there is a pile of money. Usually a gang of five or six people appears, including a woman. The liar took out a mat the size of a mop beside an old man. He put a big plastic bottle cap and some corn kernels on the dirty mat. So the scam began. Bet at least 100 yuan, guess how many popcorn beans are under the bottle cap, guess the right number of popcorn beans, and guess the wrong number of popcorn beans. Life is like a play, it all depends on acting. The two swindlers pretended not to know each other and tried their best to attract everyone's attention. As they shouted, they took out several hundred-dollar bills and bet, repeatedly guessing the number of corn beans under the bottle cap. People who don't know the truth envy them for winning money easily.