This is the common past tense.  The action happend and finished in at a specific time in the past.

For example: Yesterday I went to the library. Today, I forgot my paper.  I watched television for a half hour.  Now, when we ask questions we use the verb "do." It is not so in spanish. They always conjugate the verb.   "Did you go to the library?"  ="Went you to the library?"

Note: Sentences including when I was young etc; that encompass a block of time, like childhood, that were on going in the past are used in the Imperfect tense. Moods are also indicated with the imperfect.

Endings: AR                   

IR/ER

I ate = comer drop the er ending, add ending for Yo = Yo comí.

They ate = Ellos comieron.  You (formal) ate. = Usted comió . We ate= Nosotros comimos. However we lived= nosotros vivimos, which is the same as the present tense. You can infer whether or not it took place in the past or present by context.

Verbs ending in -car, -gar, and -zar have a spelling change in the Yo form to preserve sound.

c-->qu   buscar- Yo busqué

g-->gu  pagar-   Yo pagué

z-->c realizar-    Yo realicé

Dar and ver take IR/ER endings with no accents.

Oír has accent marks

Caer, construir and leer do so as well.

Caer- caí caíste cayó caímos cayeron

Leer- leí leíste leyó leímos leyeron

Even more, verbs in -ar and -er that have a stem change in the present do not have this stem change in the past.

pensar[ie] - pensé  contar[ue]- conté  perdir[ie]- perdí  jugar[ue] jugué are examples. (Yo form was shown)

Verbs that end in -ir that have a stem change in the present have changes in the ella and yo forms.

[e-i] sentir[ie]- yo sentí   ella-sintió   ellos- sintieron likewise with pedir[i]

[o-u] dormir[ue] Yo-dormí  ella-durmió  ellos- durmieron

More Irregulars: These verbs get stem changes, the endings are normal -ir endings for all (with no accents.)

Ser/Ir are the exact same in the preterite.

I had a dog.  Yo tuve un perro.  She came to my house.  Ella vino a mi casa.

I stood up. Me puse de pie. (I put myself on foot; ponerse de pie.)

Algunas Frases (Some Sentences)

Yo leí este libro.   I read that book.

La Argentina ganó el Mundial en 1986.   Argentina won the World cup (soccer) in 1986.

Ayer, asisití a una conferencia muy interesante.  Yeseterday, I attened a very interesting lecture.

¿Dónde te reuniste con tus amigos?  Where did you meet your friends?  (Not for the first time)

Me reuní con ellos en el Club Estudiantil.  I met them in the Student Club.

¿Qué viste en el cine?  What did you see at the movie theatre?

Vi una película del oeste.  I saw a western film. 

¿Cuándo asistó ella a la conferencia sobre arte azteca?  When did you go to(attend) the lecture over Aztec art?

Anoche, ella asistó a la conferencia.  Last night, she attended the meeting.