uses of verbs ser & estar - imperfect

Ser is used to signify equivalence or identity between
two elements:

Alberto era doctor.
Alberto = doctor. Alberto was a doctor.

María era una buena persona.
María = buena persona. Maria was a good person.

Ramón era colombiano.
Ramón = colombiano. Ramon was Colombian.

Ser is used to indicate origin:

Diego era de Perú. Diego was from Peru.
El tapete era de México. The rug was from Mexico.

Ser is used to express possession:

Esa bicicleta era de Gustavo. That bike was Gustavo's.
Las llaves eran de Julio. Those keys were Julio's.

Ser is used to talk about time:

Eran las dos. It was two.
Era la una y media. It was one thirty.

Ser is used to talk about dates

Ayer era el cuatro de junio. Ayer was the fourth of June.
Era jueves. It was Thursday.

La escuela estaba al lado del correo.
The school was next to the post office.

Estar is used to express the present progressive:

Estaba escribiendo. I was writing.
Juan estaba escuchando. Juan was listening.

Estar is used to indicate a resultant condition:
estar + past participle

Estaba cansado. I was tired.
Estábamos despiertos. We were awake.

It is very useful to use estar with prepositions to
explain where some place is.

Estaba al lado del monumento de la revolución.
It was next to the monument to the revolution.

Estaba en frente del terminal de autobuses.
It was in front of the bus terminal.

Estaba justo detrás de la parada de metro Tacubaya.
It was right behind the subway stop "Tacubaya."

Estaba en la misma calle que la embajada de los EU.
It was on the same street as the U.S. embassy.

Estaba por la iglesia de la conchita.
It's over by the church of the little shells.