By answering these two questions, the learner has a good notion of when to use should. But putting these questions into a mind map will help your learner to both visualise the concepts and retain them for future use a Rocket Spanish review. In my classes, I write up two questions side by side and circle them. The questions are, “Is it necessary?” and “Is it allowed?” I then start to make my mind map by writing the only two possible answers, yes or no? I then try to elicit the modal verbs, must, mustn’t, have to, don’t have to, can, can’t, according to the answer, and write them in the appropriate place on the mind map.