First, you get buried. Iran's Islamic Penal Code states that men convicted of adultery are to be buried in the ground up to their waists; women, up to their chests. If the conviction is based on the prisoner's confession, the law says, the presiding judge casts the first stone. If the conviction is based on witness testimony, the witnesses throw the first stones, then the judge, then everyone else—generally other court officials and security forces. Stones must be of medium size, according to the penal code: Not so big that one or two could kill the person, but not so small that you would call it a pebble. In other words, about the size of a tangerine. The whole process takes less than an hour.
Something to think about the next time Ahmadinejad declares that Iranians have superior human rights to Westerners.