How do I know when to use etre as an auxilliary verb in the perfect tense?

There are a list of set verbs which always take the verb etre as their auxilliary in the perfect tense which you will need to learn. To help you remember them you can use the mnemonic MR V DREAMPANTSMourirRenterVenirDescendreResterEntrerAllerMonterPartirArriverNaitreTomberSortirIt can help to think of all of these verbs as ways of moving from place to place or changing from state to state (eg. changing from not being born to being born).Also, all reflexive verbs (verbs with 'se') take etre as their auxiliary.It's important to remember that all verbs which take etre in the perfect tense must agree with the noun in number and gender like an adjective. Therefore to say 'they (talking about a group of girls) went out' you would say 'elles sorties' because you have to add an 'e' for being feminine and an 's' for being plural.