Many students of English as a foreign language believe that "had" is for the past activity. In the expression of "had better", the word "had" has nothing to do with the past but it is used to express "advice or suggestion".
Had better is used to express suggestion or advice that is specific. For general advice, the word “should” is often used.
Had Better is followed by infinitive without to.
Take a look at the example below:
HAD BETTER is often contracted to [‘d better]. See the example below.
Negative form of HAD BETTER:
The negative form is not placed after “had” but it is inserted after “better”
“HAD BETTER” often gives the impression that if we do not do as suggested some negative events will occur.
For general advice, “should” is often used. Take a look the sentences below.
BE BETTER OFF (+ VERB in the ING form)
The expression of better off is also used to give advice or opinion. After “better off” the verb in the ING form is used. Practice the example below: