The Preter ite Indicative Tense of Regular Verbs. 
The preterite tense de notes an action or actions that were begun in the past or that were completed in the past.
There are two sets of regular endings.
AR verbs ER verbs  and IR verbs
Cantar -- to sing

I sang yesterday.
I did sing yesterday.

 Comer -- to eat

I ate last night.
I did eat last night.

 Escribir -- to write

I wrote last Saturday.
I did write last Saturday.
Canté ayer.
Cantaste
Cantó		 Comí anoche.
Comiste
Comió		 Escribí el sábado pasado.
Escribiste
Escribió
Cantamos ayer.
Cantaron		 Comimos anoche.
Comieron		 Escribimos el sábado pasado.
Escribieron


The Preter ite Indicative Tense of Irregular Verbs.   Irregular preterite stems require only one set of irregular endings.

UV is characteristic of these stems. US and UP are characteristic of these stems.
Estar - to be

Estuv: Pret.stem

I was there.

Estuve allí.
estuviste
estuvo

estuvimos
estuvieron

 Tener - to have

tuv: Pret. stem

I had a letter.

Tuve una carta.
tuviste
tuvo

tuvimos
tuvieron

 Poner - to put

Pus: Pret. stem

I put that there.

Puse eso allí
Pusiste
Puso

Pusimos
Pusieron

 Saber - to know

Sup: Pret. stem

I knew that.

Supe eso.
Supiste
Supo

Supimos
Supieron

I is characteristic of these stems. J is characteristic of these stems.
Venir - to come

vin: Pret. Stem

I came home

Vine a casa
Viniste
vino

Vinimos
Vinieron

 Hacer - to do

Hic: Pret. stem

I did that.

Hice eso.
Hiciste
Hizo

Hicimos
Hicieron

 Traer - to bring

Traj: Pret. stem

I brought this.

Traje esto.
Trajiste
Trajo

Trajimos
Trajeron

 Decir - to say

Dij: Pret Stem

I said the truth

Dije la verdad.
Dijiste
Dijo

Dijimos
Dijeron
Irregular preterite endings do not have accent marks.
Note the following irregula r verbs are similar to some of the above verbs.
UV like Estar

Andar - Anduv:

 U like poner and saber

Poder - Pud:

 I like venir and Hacer

Querer - Quis:

 

Identical special preterite forms for ser, and ir. An "AR" verb has regular er/ir preteriet endings. Y replaces I in the third persons.
Ser - to be

Fu: Pret. Stem

I was a soldier

Fui soldado.
Fuiste
Fue

Fuimos
Fuieron

 Ir - to go

Fu: Pret. Stem

I went home

Fui a casa.
Fuiste
Fue

Fuimos
Fuieron

 Dar - to give

D: Pret. Stem

I gave thanks.

Di las gracias.
Diste
Dio

Dimos
Dieron

 Leer - to Read

Le: Pret. Stem

I did read that.

Leí eso.
Leíste
Leyo

Leímos
Leyeron
Ser and ir being exactly alike in the preterite, can be distinguished only according to their use in the sentence.
Leer keeps its regular le stem, adds regular er endings, but changes the ío and ieron endings to yó and yeron in the 3rd persons singular and plural. An accent mark is written on the í of the other personal endings.  Conjugate caer to fall, creer to believe and oir to hear exactly like leer.