What is the pluperfect (or past perfect) and when is it used?
The pluperfect is called the plus-que-parfait in French. It is a compound past tense used to describe past actions that took place prior to other past actions that are either mentioned or implied from context. (e.g. "I had already told him.")
How do you conjugate the pluperfect?
The plus-que-parfait is formed by pairing the imperfect tense of avoir or être with the appropriate past participle. For instance, the je form of parler in the pluperfect is j'avais parlé -- "I had spoken."
I had already told her not to open the door
Je lui avais déjà dit de ne pas ouvrir la porte
Note the first-person singular pluperfect form of dire. Also note the placement of déjà in between the auxiliary verb and the participle.
Marie had already left when you called her
Marie était déjà partie quand tu l'as appelée
Note the use of both the pluperfect and the passé composé. The pluperfect verb describes an action that took place before the action of the passé composé verb.
They hadn't had their coffee yet when I got to work
Ils n'avaient pas encore pris leur café quand je suis arrivé au travail
Here, the pluperfect is used together with the passé composé to describe past actions that took place at different times.
Sophia wanted to see you but she had forgotten where you were
Sophia voulait te voir mais elle avait oublié où tu étais
Here, the pluperfect is used along with the imperfect tense.
They hadn't yet done their homework when Jean came home
Ils n'avaient pas encore fait leurs devoirs quand Jean est rentré
We hadn't finished yet when our boss arrived
Nous n'avions pas encore fini quand notre patron est arrivé
He had hardly begun running when he fell
Il n'avait guère commencé à courir quand il est tombé
(formal) He had just arrived when you phoned him
Il venait d'arriver quand vous lui avez téléphoné
Recall that in the past, the construction venir de + infinitive is conjugated in the imperfect. In other words, for the immediate past, the imperfect (plus an infinitive) is used even though in English the pluperfect is used ("had arrived").
What is the past conditional and when is it used?
The past conditional is used to describe what would have taken place if circumstances had been different in the past. (e.g. "I would have left.") In other words, it is used to describe hypothetical scenarios in the past. It is often used with the plus-que-parfait and with si clauses.
How do you conjugate the past conditional?
The past conditional is formed by using the present conditional of avoir or être with the proper past participle. For example, the first-person singular form of parler in the past conditional is j'aurais parlé -- "I would have talked."
In that case, I would have left
Dans ce cas-là, je serais parti
Note the je form of the past conditional of partir.
Paul would have gone shopping, but he didn't have any money
Paul aurait fait les courses, mais il n'avait pas d'argent
Note how the past circumstances here are laid out in the imperfect tense.
(female speaker) In your position, I would have washed myself
À ta place, je me serais lavée
Note how the participle agrees with the feminine subject, since the reflexive verb takes être as its auxiliary verb.
I couldn't have seen it without my glasses
Je n'aurais pas pu le voir sans mes lunettes
Would you guys have done the same thing for me?
Auriez-vous fait la même chose pour moi?
Claire would not have gone to the party without her parents
Claire ne serait pas allée à la fête sans ses parents
We would have liked to go (there)
Nous aurions aimé y aller
Pierre and Marcel should have come
Pierre et Marcel auraient dû venir
Recall that in the conditional, the verb devoir denotes obligation or necessity. It means "should" rather than "would."
Do you think we shouldn't have left?
Penses-tu que nous n'aurions pas dû partir?
If it had not snowed, I would have walked to work
S'il n'avait pas neigé, j'aurais marché pour aller au travail
Note how the past conditional is used with a si clause in the pluperfect tense. The result clause is in the past conditional.
They would have left France if their plane had been on time
Ils auraient quitté la France si leur vol avait été à l'heure
The past conditional clause describes what would have happened/been possible, while the pluperfect si clause describes what would have had to happen (first).
Marie would not have gone to the park if she had known that it would rain
Marie ne serait pas allée au parc si elle avait su qu'il pleuvrait
Here, the pluperfect si clause describes a past hypothetical condition that is contrary to fact/what actually happened. In other words, it describes an unmet condition.
Had he known that this freeway was so dangerous, Jean would have driven more slowly
S'il avait su que cette autoroute était si dangereuse, Jean aurait conduit plus lentement
You wouldn't have found your shoes if I hadn't helped you look for them
Tu n'aurais pas trouvé tes chaussures si je ne t'avais pas aidé à les chercher
They wouldn't have done anything if I hadn't said something
Ils n'auraient rien fait si je n'avais pas dit quelque chose
If you had asked me the question, I would have responded
Si tu m'avais posé la question, j'aurais répondu
He wouldn't have met his girlfriend if they hadn't introduced him to her
Il n'aurait pas fait la connaissance de sa copine s'ils ne la lui avaient pas presentée
Recall the correct order of pronoun placement. Also note the agreement of the participle with the preceding direct object pronoun.
We would have played basketball if it had been nice out
Nous aurions joué au basket s'il avait fait beau