We use had better to give strong advice, or to tell people what to do. After had better, we use the infinitive without to.

• You had better consult a doctor.
• It is late. I had better hurry up.

Had better may suggest a threat. It is not used in polite requests.

Compare:

• Could you lend me some money? (request)
• You had better lend me some money. (order/threat)

Had better refers to the immediate future, but the form used is always past. Have better is not possible.

• Shall I go now? You had better. (NOT You have better.)

We can put better before had for emphasis. This is common in British English.

• ‘I promise I will pay you back.’ ‘You better had.’

We normally make the negative with had better not + infinitive.

• You had better not tell him.