how do i know when to use the preterite and when to use the imperfect tense in spanish ?

The imperfect tense and the Preterite tenses are the two main past tenses in Spanish, yet they are used in different situations. The preterite is used to talk about completed events or actions in the past with easily identifiable starting and end points.E.g. events that occurred within a specific time frame -  El sábado nevó todo el díaIt is also used to indicate an event or action that took place while another action (usually in the imperfect tense) was still ongoing, E.g. Cantaba cuando lleguéThe imperfect tense is used for more habitual actions or re-occurring events. It is also used for descriptions or to provide background information to an event or story, E.g. El palacio era maravillosoThe Imperfect is also used if an action in the past occurred over an extended period of time, E.g. Yo bebía té frecuentemente The last main use of the imperfect is in order to express time or age in the past.E.g. era las nueve de la noche / tenía dieci-seis años