1.不定式做主語
(1)引導邏輯主語的介詞：不定式的邏輯主語一般由介詞for引導,但下列表示人的性格行為特征的形容詞做表語時, 不定式的邏輯主語則由of引導：
absurd, bold, brave, courageous, careful, careless, clever, wise, foolish, silly, stupid, good, nice, kind, thoughtful, considerate, greedy, generous, honest, modest, polite, rude, cruel, selfish, lazy, wicked, wrong。如：
It’s clever of you to have invented such a device.
(2)不定式做主語補足語：
掌握常用不定式做主語補足語的句型。注意不定式表示的動作發生的時間，并采用相應形式。如： be said / reported / thought / believed / known / supposed + to do sth.
2.不定式做賓語
掌握要求接不定式做賓語的動詞：
afford, arrange, attempt, claim, desire, determine, expect, fail, guarantee, endeavor, intend, pledge, pretend, resolve, request, swear, tend, venture。如：
Even though the children pretended to be asleep, the nurses were not deceived when they came into the room.
3.不定式做定語
(1)被修飾的名詞前有序數詞、形容詞最高級或next, last, only, not a, the, very等限定詞時，該名詞用不定式做定語。如：
the first woman to set foot on the moon 第一個登上月球的女性
(2)如果其動詞要求不定式做賓語，相應的名詞一般用不定式做定語。如： tendency to do→tend to do, decision to do→decide to do
This book is an attempt to help you use English and recognize how it is used.
(3)如果其形容詞形式要求接不定式做補語，相應的名詞一般用不定式做定語。如： ambition to do “干……的雄心”→be ambitious to do“有雄心干……” curiosity to do “對……的好奇心”→be curious to do“對……好奇” ability to do“做……的能力”→able to do“有能力做……”
According to Darwin, random changes that enhance a species’ ability to survive are naturally selected and passed on to succeeding generation.
(4)表示方式、原因、時間、機會、權利等名詞用不定式做定語，這些名詞包括：
way, method, reason, time, place, chance, occasion, opportunity, evidence, power, right, movement, drive (運動)，effort等。如：I worked so late in the office last night that I hardly had time to catch the last bus. We appreciate your efforts to bring about a comprehensive solution to the existing problem. (5)不定代詞something, nothing, little, much, a lot習慣上用不定式做定語。如： Though we have made great progress, there is still much to be improved.
4.不定式做狀語
不定式做狀語主要表示目的、程度、結果、方式。
(1)in order to(do), so as to(do)結構引導目的狀語，so as to不能臵于句首。如： (2)so…as to, such…as to, enough…to, too…to結構做程度狀語。如：
The vocabulary and grammatical differences between British and American English are so trivial and few as hardly to be noticed.
(3)不定式做結果狀語只能出現在句子的末尾，表示不愉快的結果，有時用only加強語氣。常見的不定式動詞有find, hear, see, be told, form, give, make, produce等。如：
Greatly agitated, I rushed to the apartment and tried the door, only to find it locked.
(4)not/never too… to, too… not to, but/only too…to, too ready/eager/apt/inclined to 表示肯定意義。如：
I am only too pleased to hear from you further.