（一）不定式
1. 动词know后不能直接跟不定式作宾语，只能跟疑问词+不定式。
There isn’t any difference between the two. I really don’t know which to choose.
I don’t know whether to stay or not.
类似的动词有：show, ask, tell, explain, consider, find out, understand, etc.
注意：不定式与only连用表示一种意外或不幸的结果。
I went to see him only to find him out. 我去看他，不料他出去了。

2. 以下短语常跟不带to的不定式。
might as well　　would rather　　would sooner(宁愿)
would as soon　　had bette　　had rather (宁愿)
may just as well (还是……的好)　　prefer … rather than
rather than (而不是)　　had sooner (宁可，宁愿)
He preferred to stay at home rather than go out.
She said she had sooner live in the city than on a farm.

3. 介词but, except, save, than等后接不定式。
1) but后常跟带to的不定式，只有在下列短语中but后不带to。
do anything/everything/nothing but　　cannot help but
cannot but　　cannot choose but
The sailor did nothing but complain about the food.
Can’t you do anything but ask silly questions?
2) 当but连接两个平行结构时，会出现带to的不定式。
They went to America not to study English but to do business.
3) 在have no (any) choice/alternative but结构中，不定式带to。
I think you have no choice but to go with me.
I had no alternative but to do as you tell me.
4) 介词except, than后既可跟带to的不定式也可跟不带to的不定式。
She did nothing else than (to) laugh. 她只是哭。

4. 动词help, bid, know等既可跟带to的也可跟不带to的不定式作宾语补足语。
Will you help me (to) make the plan?
The king bids all subjects (to) pay the tax.
注意：动词know前面的时态是现在时，通常用to be作宾语补足语；若其前面为过去时或完成时，可用其它动词作宾语补足语。
I know him to be a liar.
I have never known her (to) sing so beautifully.
They knew him to have come.

5. 当不定式作宾语，其后又跟有宾语补足语时，应用it作形式宾语，真正的宾语应置于句末。常用于这一句型的动词有find, feel, think, consider, deem(相信，认为), make, believe等。
Do you consider it wise to ignore them?
I find it very difficult to study English well.

6. 以下动词常跟不定式的完成时作宾语：
seem                 suppose           mean            wish              hope               expect
promise            appear             would           happen         pretend
I meant to have telephoned, but I forgot. 我本打算打个电话，但后来忘了。
She wished to have come here last night, but she had no time.
注意：在美国英语中intended或had intended其后的不定式采用一般式就可表示希望，打算或意图未曾实现，不应用不定式的完成时，TOFEL考试将此评为错误。
I intended to come, but a heavy rain prevented me from coming.
I intended to write her a letter yesterday, but I forgot to because of the day and evening appointments that I had.

7. 以下短语常跟不定式的完成时作主补：
be believed/found/known/said/reported/supposed
be thought/understood…
He is said to have translated the book into Chinese.
You are supposed to have read the instructions.

8. deserve, need, require, want 前的主语为有生命的人或物时，后常接不定式。
She deserves to win because she was the best.
The boy needs to study hard.
注意：若主语为无生命的事物，其后常接不定式的被动式，动名词的主动式。
These flowers need to be watered at once.（… watering at once.）
This point deserves mentioning. (… to be mentioned.)

9. 当不定式与其所修饰的名词构成动宾关系，不定式又是不及物动词时，后面要加相应的介词。
He is a very good comrade to get along with.
We want to find a place to live in.

10. have与get后接不定式作宾补时，get后的宾补前应加to.
I’ll have a worker repair the door.
or:
I’ll get a worker to repair the door.

11. 不定式的逻辑主语
一般情况下不定式的逻辑主语就是句子的主语。
He studies hard to get high scores.
但有两种特殊情况：
1) 由for引出逻辑主语。
This is a very difficult for us to answer.
2) 如果形容词是指行为的性质又同时指行为的人即表示人的性格、特征等，由of引出逻辑主语，常见的形容词有：
kind　　foolish　　good　　wise　　stupid　　honest　　brave　　wrong　　right　　considerate　　rude　　boldnice　　impolite　　courageous 　　wicked 　　clever　　silly
It’s kind of you to give me so much help.
It’s foolish of you to behave like that.