1. 意思是“应该；最好”;

You had better study hard for your entrance exam.
You had better see the doctor about your cough.

2. 后接不带 to 的不定式：had better do sth;

you had better be careful.
It’s five o’clock. I’d better go now before the traffic gets too bad.

3.其用法相当于情态动词，动词 had 没有人称或数的变化。

She had better get here soon or she’ll miss the opening ceremony.
You had better show your hand when the police want.

4.常用来提出建议，语气较强，我们一般强调如果不这样做会有不好的后果。
或表示迫切的希望，警告等。

We’d better take something to eat or we will be hungry later.
You had better lock the door before you leave.

5. 该短语指的是现在或将来的情况，而不指过去。

You’d better take an umbrella or you will get wet.
I think I had better take them or they will get lost.

6. had better的简略式为：’d better 。口语里had也常常被省略。如：

It’s five o’clock. I’d better go now before the traffic gets too bad.
you better not come tonight.
It’s getting late. You’d better leave now or you will miss your bus.

7. had better的否定是had better not；疑问式是将 had 放在主语之前。如：

They had better not be late.
They had better not forget Tom’s birthday gift.