Overview - From Spanishdict.com - QUIZ

Many students have trouble knowing when to use the preterite tense or the imperfect tense since they both refer to actions in the past. There are several general rules to follow, as well as phrases to look out for. Many phrases use only one tense or the other, so memorizing them is very helpful in figuring out whether the use a verb in preterite or imperfect!

General Preterite Uses

Generally, the preterite is used for completed actions (actions that have definite beginning and end points.) These can be actions that can be viewed as single events, actions that were part of a chain of events, actions that were repeated a very specific number of times, or actions that specifically state the beginning and end of an action.

General Imperfect Uses

The imperfect tense is generally used for actions in the past that do not have a definite end. These can be actions that are not yet completed or refer to a time in general in the past. It can also be used to talk about:

actions that were repeated habitually
actions that set the stage for another past tense event
time and dates in the past
for telling a person’s age in the past
to describe people (characteristics) in the past
to communicate mental or physical states in the past