Heaven.
After the baptism came the selection of choirs. This happened when a a large group of higher power angels met with each other to organize the younger ones into different choirs: groups in which they would perform the orders of Heaven together. Although it wasn't necessarily a celebrated event, it was just as important for young angels as the baptism. This was because it was a time for judgement and selection. It was a time to prove one's worth.
Back in the days before the war with Hell began, choirs were used in all sorts of different missions. Some would handle the domestic and civil affairs of Heaven, some would look after the happenings of Earth, and some would aid with maintaining the balance between the three realms. Most fell into the first or second category, as those positions were where the most hands were needed. Very few angels, such as Ophaniel or Lucifer, ever actually ended up working alone.