The verb ser (conjugation) means "to be". It is completely irregular in the imperfect tense.
I used to be
you used to be
you/he/she used to be
we used to be
you guys used to be
you all/they used to be
The imperfect tense is used to refer to actions in the past that occurred repeatedly or actions that occurred over an extended period of time. The verb ser may be translated to English as "used to be" or "was" or "were".
Sentences using ser in the imperfect tense
Yo era travieso.
I used to be mischievous. (masculine)
Yo era mimado.
I used to be spoiled.
Tú eras la secretaria de la oficina.
You used to be the secretary in the office.
Juana era alta y bonita.
Juana was tall and pretty.
Nosotros caminábamos a la escuela cuando éramos niños.
We used to walk to school when we were children.
Nosotros éramos policías.
We used to be policemen.
Vosotros comíais de todo cuando erais niños.
You all used to eat everything when you were little.
¿Vosotros cantábais en el coro cuando erais jóvenes?
Did you all used to sing in the choir when you were young?
Todos sus primos se llevaban muy bien cuando eran niños.
All of their cousins got along really well when they were children.