How do i know when to use the imperfect or preterite tense?

The preterite and the imperfect are both tenses used to express past actions in Spanish, however it is important to remember how to use each one and when to use them, as it can be confusing! Generally speaking, the preterite tense is used for completed actions, or that are implied as such. For example:Juan habló de la una hasta las dos. (Juan spoke from one o'clock until two o'oclock). Here, the preterite tense is used as the beginning and the end is clearly stated (1-2).However the tricky thing is that the ending is not always clear, when the preterite tense should still be used. For example:Juan habló con la estudiante. (Juan spoke with the student). Although the end here is not necessarily specified, it is implied from context that there was a beginning and end to the conversation. When it comes to the imperfect tense, it is used in a more general sense for actions that are not seen as completed. For example:Las chicas hablaban en inglés. (The girls used to speak in English). There is no definite beginning or end here, and so the imperfect tense is used to express when the action took place without naming any specifics. The imperfect tense is also used when talking about things you used to do (e.g when you were younger). Again, these things do not necessarily have a specified beginning or end. For example: Cuando era pequeña jugaba al fútbol. (When i was little, i used to play football).