When should I use the imperfect tense and the preterite tense?

We use the imperfect to decribe actions in the past which used to happen regularly, for example: Iba al cine. This can be translated as, "I used to go to the cinema". It is also used to describe things that happened in the past for an ongoing time, but we are not exactly sure how long. For example: Quería ir al cine. This can be translated as "I wanted to go to the cinema". We use the preterite to refer to specific events that happened in the past once. For example: Ayer, fui al cine, This can be translated as "Yesterday, I went to the cinema". Both tenses can also be used together to describe and interrupted action. The imperfect is used to describe the action which is interrupted and the preterite to describe the interupting action. For example: Ayer, iba al cine y mi madre me llamó. The translates as, "Yesterday, I was going to the cinema and my mother called me".