If you are traveling to Asia (Thailand, Cambodia, Laos, Myanmar) you might be approached by a monk. After he has introduced himself and you have enjoyed a pleasant chat, he will tell you about his temple. He will then ask you for a small contribution towards his studies or the building of a new pagoda.
How to avoid: don’t give him anything, as real Buddhist monks do not approach foreigners in that way. The scammer just waits for tourists who don’t know much about their culture.