1. be+to do表示“将要做……”
He is very happy to be a student in the university. 将要成为大学生，他感到非常高兴。
2. have (has) + to do表示“不得不做……”
It is late now. He has to go home. 天晚了，他不得不回家去。
I have to stop my car and wait for the policeman. 我不得不停车等那个警察。
3. there be ... + to do表示“有……要做”
There is nothing important to do today. 今天没有什么重要的事要做。
There are lots of letters to post now. 现在有许多信要寄。
4. be about+to do表示“正要做……”
She was just about to leave when someone called her. 正要离开，忽然有人给她打电话。
Hurry up!The match is about to begin. 快点，比赛就要开始了。
5. only+to do表示“却……”
She went home in a hurry only to find that nothing happened there. 她匆忙回家，却发现那儿什么事都没有发生。
He lifted a stone only to drop it on his own feet. 他搬起了石头却砸了自己的脚。
6. so as(not)+to do表示“为了(不)……”
She worked hard so as to be a college student. 为了上大学，她努力学习。
He went to work early so as not to be late. 为了不迟到，他很早就去上班了。
7. enough+to do表示“十分……，足够……”
The girl isn't old enough to go to school. 这个女孩还不到上学的年龄。
8. It is (was)+形容词 + of(for)sb. + to do ... 表示“(某人)做某事很……”。
It is wise of you to do so. 你这样做很明智。
It's very hard for you to get there on foot. 对你来说，步行到那儿是非常艰难的。