1.stop to do sth. 和stop doing sth.
“stop to do sth.” 表示停止做其它事情而去做“to do sth.”所表示的事情，可以将“to do sth.”理解成“stop”的目的状语：“stop doing sth.”表示不做“doing sth.”所表示的事情。
例如：“Stop talking. Let's begin our class.”said the teacher. 老师说：“别说话了，让我们开始上课。”
We have kept doing our homework for a long time. Let's stop to listen to music. 我们做家庭作业很长时间了，让我们停下来听听音乐。
2.have sth. done.(过去分词)(让别人)做某事
例如：I had my hair cut yesterday afternoon. 我昨天下午理了发。
My computer can not work now. I must have it repaired. 我的电脑有故障了，我必须让人修好它。
3.forget to do sth.和forget doing sth. (remember to do sth. 和remember doing sth.)
“forget to do sth.”表示将来不要忘记做某事，谈的是未来的事情：“forget doing sth.”表示忘记过去应该做的事情。
例如：“Don't forget to do your homework.”said the teacher before the class was over.
老师在下课前说：“不要忘记做家庭作业。”
“I'm sorry. I forgot doing my homework. May I hand it in this afternoon，Mr. Chen?”said Li Ming.
李明说：“对不起，我忘记做家庭作业了。我今天下午交好吗，陈老师?”
4. 感官动词后接不带to的不定式或者现在分词的区别
例如：see sb. do sth.看见某人(经常)做某事 和see sb. doing sth.看见某人(正在)做某事
I often see him do exercise in the morning. 我经常在早晨看见他锻炼身体。
When I was walking in the park，I saw him drawing a picture there. 当我在公园散步的时候，我看见他正在那里画画。
5. 介词后面一般接动名词。同学们要特别注意介词to和不定式符号to的区别，例如下面的词组一定要记清：
prefer doing sth. to doing sth. 喜欢做……不喜欢做……
look forward to doing sth. 期待/盼望做某事
make a contribution to doing sth. 为……做出贡献
6. 在主动语态中，感官动词(see，hear，feel，watch等)和使役动词(make，have，let等)要求接不带to的不定式做宾语补足语，而在被动语态里，不定式要带上to.
例如：The boss often made the workers work 10 hours a day.
The workers were made to work 10 hours a day.
She was heard to use strong language. 听说她骂人了。
7.常用的几个和不定式有关的句型：
Why not do sth?为什么不做某事?
It takes/took sb. some time to do sth. 做某事花了某人多长时间。
It is/was +形容词+(for sb.)+to do sth. 做某事(对某人来说)怎么样。
8. 现在分词和过去分词做定语的区别
A. 现在分词含有正在进行的意思，而过去分词含有被动或者已经完成的意思，如：
a developing country 发展中国家 a developed country 发达国家
boiling water 正在沸腾的水(一般情况下水温为100℃) boiled water 开水(已经烧开的水，水温可以依然很高，也可以是凉白开)
a boy named Jim 一个叫Jim的男孩
B. 有些动词的现在分词和过去分词都具有形容词特征，但是它们的意思有区别。它们的-ing形式往往用来说明事物的特征;他们的-ed形式表示被动的意思，用来说明人的情况。
I am interested in this interesting story. 我对这个有趣的故事感兴趣。
I am moved at the moving sight. 我被这动人的情景感动了。
They were amazed at the amazing facts. 他们对那些令人惊异的事实感到惊奇。
