The Past Perfect: Meaning

The speaker is looking back to an action that happened before another action in the past.

It had stopped raining so they continued with the picnic. 

I had cooked dinner earlier in the day. 

After John had cooked breakfast, he fell asleep. 

The Past Perfect: Forms

Affirmative (Positive)

We had won 3 gold medals by 1pm on the first day.

Form: Subject + had + verb (past participle)

Negative

I had not eaten fish and chips until I came to the UK.

Form: Subject + had + not + verb (past participle)

Question (Interrogative) 

Had you ever played baseball before you moved to the USA?

Form: Had + subject + verb (past participle)?