Wah How to use "Ought to"

You can use ought to to give advice or tell someone what to do.

• You ought to go to bed early. (You should go to bed early.)
• Ought we to have lunch now? (Do you think it's a good idea for us to have lunch now?)
• We oughtn't to leave this door unlocked.

Ought, like should, is a modal verb:
It does not take an -s in the third person. (oughts)
There is no past tense or gerund. (oughted,oughting)

However,unlike should, ought is followed by to.
You can use ought to have + Past Participle to talk about things in the past which were supposed to happen but didn't.

• You ought to have remembered your wife's birthday. (But you forgot.)