Past Perfect Tense - Regular Verbs

When to use it: For describing what has happened, what someone has done or what happenend in the past.
How to form it: You need to remember that there are two parts to a perfect tense verb - the auxiliary verb and the past participle.
The auxiliary verb shows who or what did the action and the past participle shows what happened.

Here the auxiliary verb is avoir. For regular -er verbs, the past participleis formed by replacing the -er ending of the infinitive with -é. 
e.g. travailler > travaillé:
j'ai travaillé = I worked 
tu as travaillé = you worked 
il a travaillé = he worked 
nous avons travaillé = we worked 
vous avez travaillé = you worked 
ils ont travaillé = they worked
Notice that the past participle does not change. 
It is the auxiliary verb that changes.

In a similar way to -er verbs, we can alter regular -ir and -re verbs.
Form -ir verbs by taking the -ir off the end of the infinitive and adding -i.
Form -re verbs by replacing the -re of the inifinitive with -u.
Examples: 
j'ai joué = I played 
nous avons choisi = we chose 
ils ont perdu = they lost 
tu as regardé = you watched 
elles ont fini = they finished 
vous avez quitté = you left