Let’s continue the modal verbs series with should / shouldn’t. This post has been improved by Mr. Kimmo Kosunen.
Use should / shouldn’t + base form of a verb to give somebody advice or say what you think is the right thing to do.
Note: Should/shouldn’t is often used as a form of criticism, especially with the negative: You shouldn’t drive so fast! This also depends how the speaker says it – does he sound friendly or as if he’s criticizing…
I think you should teach for another school.
The Romanian government should do more for the country.
She should buy a new motorbike; she always seems to have problems with this one.
She shouldn’t drive so fast.
should / shouldn’t + base form is the same for all persons
An alternative of should is ought. Personally, I don’t use ought.
The two forms (should and ought) are almost always used interchangeably but some consider that ought to implies a stronger obligation than should, while others think that ought to is old-fashioned and may always be replaced by should. And when something sounds old-fashioned, it almost automatically also obtains a more formal register.
The only situation I can think of when ought to cannot be replaced with should is in the British English usage of should in the meaning of if:
Should the visitors arrive early, we can have lunch with them. (Not common in American English but often used in British English).
Ought the visitors to arrive early, we can have lunch with them.
The learners of English should remember ought always goes with to.