How do I form the imperfect?

The imperfect tense is used for ongoing actions (e.g. was doing) or actions done regularly in the past (e.g. used to do). It is formed by taking the endings off a verb to form its "stem". For -ar verbs (e.g. hablar which becomes habl) we add these endings-:abaabasabaábamosabaisaban
For -ir and -er verbs (e.g. comer and vivir) we add these endings:íaíasíaíamosíaisían.