Should and ought to
‘Should’ and ‘ought to’ are basically the same, although ‘should’ is much more widely used than ‘ought to’. The negative and interrogative forms of ‘ought to’ are becoming increasingly rare. Both ‘should’ and ‘ought to’ are used to talk about obligation and duty and to give advice. One way of getting the meaning of ‘should’ across to learners is to contrast its meaning with that of ‘must’ and ‘have to’ as the degree of obligation is considerably less, e.g. ‘I have to go to the doctor’ as compared to ‘I should go to the doctor’.
It is probably a good idea to practise the above verbs using a generative context, i.e a simple context that can generate lots of examples. In the case of ‘should’ and ‘shouldn’t’, you might ask your learners to think of things they should and should do if they want to improve their English. Answers might include ‘You should read a lot in English’, ‘You should learn vocabulary in context’, ‘You should talk to English people’, ‘You shouldn’t talk Arabic in class’ and ‘You shouldn’t translate everything’. Other simple contexts where you give advice might include how to lose weight, what to do if you have a bad cold, how to give up smoking, how to be successful at an interview and so on.
At higher levels, it is more appropriate to contrast different modal verbs and to concentrate on nuances of meaning. At lower levels it is probably best to concentrate on the main meaning of each modal verb rather than to confuse learners by introducing too many meanings at once. In the case of ‘must’, for example, its use for expressing deduction or concluding that something is certain, as in ‘The keys must be on the kitchen table’, is a useful one but is arguably confusing for learners at lower levels, particularly as the negative form is ‘can’t’ and ‘not ‘mustn’t’.