As a modal verb, had better does not change its form for tense, person, etc. We use it to recommend action or give advice.

  • You had better clear up the mess before mum returns.
  • At your age, you had better have regular check-ups.
 

We can also use had better to issue warning or make suggestion about something bad that is likely to happen. We can use should/ought to to replace had better without affecting the meaning.

  • You are coughing loudly.
  • You had better see a doctor.
  • You should/ought to see a doctor.
  • I am overeating.
  • I had better go on a diet.
  • I should/ought to go on a diet.
  • We think she had better not/should not/ought not to befriend him. He’s a drug addict.