Affirmative:

Subject + Aux.Verb + V(past part..) + Compl.

• I'd visited the Louvre before so I knew where the Mona Lisa was.
• They'd studied English before they went  to London.

Negative:

Subject + Aux.Verb + Not + V(past part..) + Compl.

• I hadn't visited the Louvre before so I didn't know where the Mona Lisa was
• They hadn't studied English before they went to London.

Interrogative:

Yes/No Question

Aux.Verb + Subject + V(past part..) + Compl.?

• Had your teacher corrected the exam before you noticed?

       Yes: - Because she had worked really hard to correct it 

        No: - She hadn't 

Inf. Question:

W.H. + Aux.Verb + Subject + V(past part..) + Compl.?

• Who had you gone to the cinema with when you left?
• What had you eaten when he came?