Any student of the Spanish language will know that when it comes to deciding between the Spanish Preterite or the Imperfect past, there’s always a moment of confusion in which we have to trawl through our lists of rules and regulations to know which tense to use.
What makes it worse is that some text books bombard us with enormous lists of rules written in a language clearly designed to either confuse or strike fear into the average learner.
So, with that in mind, let’s see if we can demystify these two tenses a bit.
NOTE: I’m not going to talk about the structure or conjugations of these tenses, so if you are not sure, take a look at them now and then join me again.
A Useful Metaphor.
Imagine you were in a theatre watching a theatre production. As you sat there you listened to the music playing from the orchestra, you watched the lights changing place and colour and highlighting the background scenery. Meanwhile, all the extras were dancing in the background.
THIS WAS THE SPANISH IMPERFECT PAST.
Then, the two main characters came on stage, they stared at each other, and began to speak. The real action had begun.
THIS WAS THE SPANISH PRETERITE PAST.
When we tell a story about the past, we use the Imperfect to set the scene and then we use the Preterite to recount the action.
GREAT TIPS SO YOU ALWAYS GET IT RIGHT.
THE SPANISH PRETERITE PAST.
The Preterite Past is what we could call a ONE OFF tense., like: ‘I ate’, ‘I went’, ‘we spoke’, ‘they arrived’ etc.
The Preterite Past is TOTALLY MEASURABLE and is as though the speaker is wrapping the past event inside a BUBBLE OF TIME.

To know whether what you are about to say is Preterite then all you do is ask TWO SIMPLE QUESTIONS about the event.
1, HOW MANY TIMES DID IT HAPPEN?
2, FOR HOW LONG DID IT GO ON?
If you can answer these questions with some certainty the the past WILL BE PRETERITE.
THE SPANISH IMPERFECT PAST.
The Imperfect Past in Spanish is everything that the Preterite isn’t. It’s pure description. It does absolutely no measuring. We use it to SET THE SCENE in the lead up to providing the Preterite action.
The Imperfect Past is immeasurable like an EVENT IN A LONG UNBROKEN LINE.

To know when to use the Imperfect Past, you need to look out for the following in your English sentence:
WAS …… ING
WERE ……ING
USED TO
e.g. I was talking to Pedro. We were looking at clothes. I used to live in Spain.
Sometimes, none of the above appear in the sentence in English. So what do you do?
You can simply apply the Preterite questions and if you can’t reasonably measure it, then it will be Imperfect. Also, you can try and add the words “USED TO” to the sentence. If it still makes sense, then it will be Imperfect.
e.g.
When I lived in Spain, I ate breakfast on the patio.
We could put ‘used to’ into this sentence and it will make sense. So this sentence will be Imperfect.
Of course, you can choose the tense according to what you want to say, too. By changing the tense, you will change the understanding of your listener. However, if there is any question of measuring the past, it will be the Spanish Preterite.
Hopefully this will help you begin to order your thoughts in a more simplistic way. Watch out for the up and coming video on this important subject.