In the United States, someone should wear a lapel pin near their heart on the left side. The only exception in the U.S. is when a specific organization requires a different placement and they will relay this information to an individual.
Individuals wearing at least two pins, for promotional or decorative purposes, should consider the type of pins they are wearing. For example, those wearing an American flag should stick to the proper placement, because this is patriotic and respectful to the flag. When it comes to promoting a business or cause, the primary pin should go near the heart and the others where the person wants them.