It is customary to place the pin on the widest part of one's suit's left lapel. However, some professions or organizations may have different protocols for wearing a lapel pin. Flag pins must be worn on the left lapel close to the heart.
While some lapel pins are used as fashion accessories, others are used to symbolize achievements or membership in exclusive organizations like professional associations, sororities and fraternities. If one is not wearing a jacket, he should place the pin at the center of the tie. If someone is wearing a shirt without a tie, the person should place the pin on the left side of the shirt.