You have to think of the order, but it's not that difficult: the "older" thing that happened first is in the past perfect, and the "newer" thing that happened second is in the simple past. Example:
"I had fallen asleep before the phone rang."
2014年9月30日
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Hi Ala, it might help you to remember that a past perfect event provides a "historical context" for a past simple event. Sometimes it can even explain why a past simple event happened. These tenses (along with past continuous) all work together. It's much more than the order of events.