1. Used as a modal auxiliary verb. Example :
He'd better not come. ( It would be a bad idea for him to come.)
2. Always followed by a verb in the infinitive without 'to'. Example :
You had better BE on time. (You must or should be on time.)
3. ALWAYS formed from the auxiliary verb 'have' in the past simple . Example :
She had better be ready for next week's meeting. She really must be ready for next week's meeting.