when do you use the preterito tense

Question

When do you use the pretérito tense in spanish?

Answer 1

I have always looked at it like this.

An action started AND completed in the past gets the preterit. Also if the time frame is set in the sentence use the preterit.

The exception to the above is actions started and stopped in the distant past take the imperfect. Also, actions that are intermitant (start and stop) or start in the past and continue into the present take the imperfect. When an ongoing action is interrupted by a present action use the imperfect as well.

Simple rules that will not be correct in every situation but will be correct most of the time.

Answer 2

Here's some examples that might help to show the difference between the pret and imp tenses: (not all meanings are shown but I'll just highlight the obvious ones)

Comí una manzana. Pret, completed action in the past

I at an apple.

Comía una manzana. Imp. ongoing action in the past

I was eating an apple.

Llegó a las cinco.

He arrived at 5 o clock.

Todavia llegaban (imp - ongoing action) cuando empezo (pret completed action) la película.

They were still arriving when the movie started.