The passé composé with 'avoir' - when should you use it and how do you form it?

The passé composé in French (perfect tense) is a type of past tense, which is used to refer to completed actions in the past. For example, in English: He played in a football match and his team won. They asked me to help them with their homework. I ate in a restaurant with my family to celebrate my birthday. The formula for forming the passé composé in French is: SUBJECT PRONOUN & PRESENT TENSE OF AVOIR (the auxiliary verb) + PAST PARTICIPLE.  1). The subject pronoun with the appropriate present tense of ‘avoir’: J’ai, Tu as, Il/elle a, Nous avons, Vous avez, Ils/elles ont. 2). The past participle is formed depending on which group the verb comes from. For regular –er verbs: remove –er, and add é (Eg. 'aimer' becomes 'aimé'). For regular –ir verbs: remove –ir, and add i (Eg. 'finir' becomes 'fini'). For regular –re verbs: remove –re, and add u (Eg. 'vendre' becomes 'vendu'). So, if we put these two components together: J'ai mangé une pomme. = I ate an apple. Elle a fini ses devoirs. = She has finished her homework. Ils ont vendu leur maison. = They sold their house. Important points: 1). When ‘avoir’ is the auxiliary, the past participle remains the same – it never changes its ending to agree with the subject. 2). Some verbs take ‘être’ as their auxiliary in the passé composé (often verbs to do with motion). In this case, the past participle agrees with the subject in number and gender. Add an ‘e’ (feminine) and/or ‘s’ (plural) accordingly. 3). Some verbs have irregular past participles. For example, the past participle of ‘faire’ is ‘fait’. It is important to learn these irregular ones.