最好不做某事是had better not do sth 还是had better not to do sth?...
had better not do sth
  had better(常简略为'd better)是一固定词组,had better"最好",用于表示对别人的劝告、建议或表示一种愿望。其用法有以下几点:
  一、had better后面必须跟动词原形。
  had better后跟动词原形(即不带to的不定式),构成had better do sth.句型。
这里的had不能用have来替换。如:
  You'd better go to hospital at once.你最好立即去医院看病。
  Tom, you'd better go there today.汤姆,你最好今天去那儿。
  二、主语不论是第几人称,句子不论是什么时态,都要用had better的形式。如:
  Now you(he,we) had better listen to the teacher.你(他,我们)现在最好听老师讲。
三、had better可用于的时态。
  1.had better用于指现在。如:
  Now you had better listen to the radio.你现在最好听收音机。
最便宜的汽车  You had better be quiet.你最好安静一些。
  2.had better用于指将来。如:
  You had better start tomorrow.你最好明天动身。
We had better buy the more expensive one. It will last much longer and so it will be cheaper in the end.我们最好还是买贵些的,它更经久耐用,所以到头来,它还是更便宜些。
  3.had better用于进行式,表示讲话人提出建议时,动作正在进行。如:
  We had better be watching the TV play.我们最好现在就看到电视剧。
  We had better be starting back now.我们最好现在就动身回去。
  4.had better + have + V-ed可表示"本该做而没有做的事"。如:
  You had better have done it .如果你把那件事办妥就好了。(但实际上你没有那样做)
  You had better have stayed with us .要是当时你和我们呆在一起多好啊。(实际上没有)
四、had better的否定式。如:
  常用的否定形式是将否定副词not直接放在had better的后面。如:
  You had better not miss the last bus.你最好不要错过末班公共汽车。
  You had better not leave for Nanjing the day after tomorrow.你最好后天不要动身去南京。
  注意:否定副词not绝不能放在had的后面。如:不能说:You hadn't better go.而应该说:You had better not go.
五、had better的疑问式。
  had better通常不以普通疑问句的形式出现。但有时用于否定疑问句,常用Hadn't+主语+be
?结构,作为一种劝告形式,比肯定形式的语气更婉转一些。如:
  Hadn't you better take an umbrella?你不认为该带一把伞吗?
  Hadn't you better ask him first?你不认为该先问问他吗?
六、had better在反意疑问句中。
  在反意疑问句中,疑问部分一般用"had+主语?",但有时可用"will you?"表示一种请求或建议。如:
  You'd better not go out today, had you? 今天你最好不要外出,好吗?
  I must stay at home this afternoon. You had better come to my house, will you?今天下午我必须留在家里,你最好来我家,好吗?
七、在祈使句中,had有时可以省略。如:
  Better not do it .最好别做那事。
  Better not wait for them.最好不要等他们。
  八、had better的被动式。
  You had better do it.->It had better be done.
  You had better have done it.->It had better have been done.
九、had better在间接引语中的用法。
  在直接引语变为间接引语的过程中,had better同第一人称或第三人称连用时,保持不变;had better同第二人称连用时,可以保持不变,也可用advise+宾语+不定式(宾补)来表示。如:
  He said, "Ann had better hurry."->He said (that) Ann had better hurry.
  He said, " I had better hurry."->He said (that) he had better hurry.
  He said to me," You had better hurry." ->He said (that) I had better hurry.->He advised me to hurry.
十、had better在表示对别人劝告、建议时,不宜用于与陌生人、长辈及上级的交谈中。
  对长辈说话时,最好不用had better。比较有礼貌的说法是:It might be better ;
  It would be better 。如:
  It might be better for you to help me,Grandpa.爷爷,您最好能帮我一下。
[练习]
  下列各句都有一处错误,请改正。
  1.You'd better to wait for me at the school gate.
  2.I have better write to him now.
  3.You had not better go there.
  参考答案:1.去掉to。2.have应改为had。3.将not置于better后面