There is a set number of verbes which use "être" as their auxiliary verb. These verbes are also called verbes de la gare. They are associated with movements of people and you can use them when in a train station (gare in French). For example, arriver à la gare, descendre le train, monter le train, rester sur le train, départer, aller, arriver, sortir, partir, entrer, rentrer, retourner, tomber. The three only verbes which you cannot immediately connect to a train station are: being born (naître), becoming (devenir) and dying (mourir). These you hae to know by heart. However, these are conntected to the human life cycle and therefore easy to remember. Also remember to change the verb when using être in the past tense. The verb changes according to gender and number of people doing it.