The principal usage of the past conditional is to express future events in the past, following the tense agreement of past tenses. This use differs from English, since in Italian we employ the past conditional, whereas in English we would use the present conditional instead. In this case, a verb conjugated in the past tense always precedes the past conditional.
Mentre pensavo alla mia ragazza sapevo che mi avrebbe chiamato. "While I was thinking about my girlfriend, I knew she would call me."