When is it appropriate to use the imperfect and preterite?

The preterite is generally used for an action that has been completed in the past, which has a definite beginning and end point Example:Anoche fui a la fiesta The imperfect is generally used for an action that does not have a definite end point, including a time in general in the past or an action that isn’t completed yet. It is also used to describe: habitual actions, times and ages, actions that are interrupted by another, characteristics, mental or physical statesExamples: Cuando era pequeña, jugaba al fútbol Ella tenía 25 años cuando se casó con su novioCaminaba por la calle cuando vi a mi amigaMi abuelo era muy alto Hacía mucho calor esa noche I would then help the student to write their own sentences in the past using either the preterite or imperfect, referring back to the list.