Modals for advice (should, ought to, could, had better)

ModalsShouldOught toCouldHad better
Uses“Should” is used to make suggestions or ask for advice. 

“Ought to” is used to make a suggestion. 
NOTE: “Ought to” is not very common because it is old-fashioned and very formal. ‘Should’ has the same meaning and is used more often. 


“Could” is used to make suggestions. It is less strong than “should”. When you use “could”, you offer possibilities. 
NOTE: Never use “could” to ask for advice. “Could” is used for permission. 
“Had better” is used to make strong suggestions. This means there will be consequences if the suggestion is not followed. 
NOTE: If you use the contraction ” ‘d better”, the suggestion is stronger. 
FormalityNeutralFormalFormalInformal
Examples
Giving advice: You should exercise more. 
Asking for advice: 
What should I do?
Should I put these products on sale?
Making a suggestion:
You should be friendly with the secretary.
Making a suggestion:
The boss ought to fire him, he is so lazy.
Making a suggestion:
We could try calling his phone. 
Contrast: 
We should try calling his phone. 
“Should” here is stronger. We ‘need’ to try calling his phone. “Could” is just a possibility. The person is not sure. 
Making a suggestion:
We had better not be late to the meeting. 
Making a stronger suggestion: 
You’d better finish this report before 5:00pm.