How do you form the Perfect Tense? (passé composé)

The 'Perfect Tense' is made of two parts: The 'AUXILIARY' (form of avoir/ être) + the 'PAST PARTICIPLE'
You pick the auxiliary according to the subject (ie. if you want to use 'nous' then the auxiliary will be 'avons' / 'sommes' )You then decide whether you need to use 'avoir' or 'être'- the easiest way to decide this, is whether the verb is in ' DR MRS VANDERTRAMP' (devenir, revenir, monter, rentrer, sortir, venir, arriver, naître, descendre, entrer, retourner, tomber, rester, aller, mourir, partir.) All 'DR & MRS VANDERTRAMP' verbs take 'être' and if it's not one of those verbs- you use 'avoir'You then make the 'past participle.' - You make this by taking the infinitive (dictionary form of the verb,) taking off the ending: -er, -ir, or -re, and adding the correct ending. If the verb ends in -er (ie. jouer) you add -é (to make joué,) if the verb ends in ir (ie. finir) you add -i (to make fini,) if the verb ends in -re (ie. vendre) you add -u (to make vendu)
Unfortunately, there are a few irregulars, which you should be able to recognise, a few examples:avoir= euboire= bucomprendre= comprisconnaître= connucroire= crulire= luprendre= pris
The last thing to remember, if your auxiliary is 'être' (you're using a 'DR & MRS VANDERTRAMP' verb) then your past participle must AGREE with the subject.-this means you may need to add something to the past participle:je suis alléif it's MASCULINE= no endingif it's MASCULINE PLURAL= 's' (nous sommes allés)if it's FEMININE = 'e' (elle est allée)if its FEMININE PLURAL= 'es' (elles sont allées)