When do you use the verb etre to form the perfect tense?

It is essential to think about the verb being used when conjugating a verb in your written (and spoken) French. As a general rule you can use the acronym MRS VAN DER TRAMP to remember the most common French verbs which take etre, and it also helps to think about these words in terms of movement- if your subject is moving in any way (for example, entrer, monter, decendre) then the auxilary verb will be etre, and if this is the case don't forget your agreements! Unlike avoir verbs, etre verbs must agree with the subject.