[had + past participle]
USE 1 – Completed Action Before Something in the Past

Examples:
- She had never seen a bear before she moved to Alaska.
 - I had never seen such a beautiful beach before I went to Kauai.
 - I did not have any money because I had lost my wallet.
 - Tony knew Istanbul so well because he had visited the city several times.
 - Had Susan ever studied Thai before she moved to Thailand?
 - She only understood the movie because she had read the book.
 - Kristine had never been to an opera before last night.
 - We were not able to get a hotel room because we had not booked in advance.
 - A: Had you ever visited the U.S. before your trip in 2006?
 - B: Yes, I had been to the U.S. once before.
 
USE 2 – Duration Before Something in the Past (Non-Continuous Verbs)

- By the time Alex finished his studies, he had been in London for over eight years.
 - They felt bad about selling the house because they had owned it for more than forty years.
 
MPORTANT Specific Times with the Past Perfect

example: She had visited her Japanese relatives once in 1993 before she moved in with them in 1996.