PAST PERFECT

It is a tense that expresses actions that have taken place in the past, but in a less recent past than is expressed in the Present Perfect.
Interrogative: Had+ subject+ verb( past participe)....
Negative: Subject + had not+ verb( past participe)...
Affirmative: Subject+ had+ verb( past participe)....

there are some exercises:  
http://www.curso-ingles.com/ejercicios-test-ingles/past-perfect.php