In french when do you use etre or avoir for past tense verbs?

Answer 1

While using the passé composé, most verbs are conjugated with avoir. However, there are many verbs that are usually associated with "coming and going" that take the être form. Also, all reflexive verbs (like s'amuser or s'appelle) are conjugated using être in passé composé. Verbs in the past tense that take the être form must also agree with the subject of the sentence, by adding an e (feminine), s (masculine plural), or es (feminine plural) at the end of the verb, for example "Il est né" (He was born) or "Ils sont nés" (they were born) vs. "Elle est née" (She was born) or "Elles sont nées" (They were born) The list of verbs that take the être form is as follows:

(The list is from the wikipedia page on the passe compose, it's not mine)

1. devenir - to become - devenu
2. revenir - to come back - revenu
3. monter - to climb - monté
4. rester - to stay - resté
5. sortir - to exit - sorti
6. venir - to come - venu
7. aller - to go - allé
8. naître - to be born - né
9. demeurer - to abide - demeuré
10. descendre - to descend - descendu
11. entrer - to enter - entré
12. retourner - to return - retourné
13. tomber - to fall - tombé
14. rentrer- to re-enter- rentré
15. arriver - to arrive - arrivé
16. mourir - to die - mort
17. partir - to leave - parti
18. passer - to pass by (this case only) - passé
19. décéder - to decease

Answer 2

You use "être" as the auxiliary verb for past tense verbs that indicate movement or a change in state, such as "to go" (aller) or "to become" (devenir). You use "avoir" as the auxiliary verb for most other past tense verbs that do not indicate movement or a change in state, such as "to eat" (manger) or "to write" (écrire).