This unfortunately pretty much rules out the romantic beach weddings in the Caribbean that are all over TV.
Luckily, as with many practices of the Church, the Church has explicitly stated guidelines for marriage in the Greek Orthodox Church.
While non-Orthodox Christians can marry in the Orthodox Church, an Orthodox Christian is not allowed to marry in a non-Orthodox Church or ceremony.
If an Orthodox Christian does get married outside of the Orthodox Church, then they are in effect excommunicating themselves from the Orthodox Church.
But do not panic, non-Orthodox friends are allowed to be members of the general wedding party, but are not allowed to be Koumbaros or Koumbara.
Finally, the Church lists days when the sacrament is prohibited: It must also be noted that a non-Orthodox Christian who marries an Orthodox Christian does not automatically become an Orthodox Christian.