When do I use should and must?

We use should for advice, or a recommendation:

You should go to the new restaurant in the mall, the prices are good and the food is delicious!

We use must/have to to insist that a person do something. There will be a bad consequence if the person doesn’t do this action:

My sister can’t come, she has to study. If she doesn’t pass her exam, she’ll have to repeat the school year!