SHOULD
Juan got 05 on his homework. He should spend more time on his homework.
If you have got toothache, you should go to the dentist.
You are very fat. You should practice sport.
OUGHT TO
You ought to eat more vegetables and fruit.
The children ought not to go alone to the park.
He ought to be more careful when driving.
MUST
If you want to play, first you must finish your homework
You will have exams in two weeks. You must study harder.
You cannot go out. You must stay at home because you have fever.