1.stop to do　停止，中断做某事后去做另一件事。
stop doing　停止做某事。
　　They stop to smoke a cigarette.　 他们停下来，抽了根烟。
　　I must stop smoking.　　　　　 我必须戒烟了。

典型例题
　 She reached the top of the hill and stopped ___　on a big rock by the side of the path.　
A. to have rested　B. resting　 C. to rest　D. rest
答案：C。由题意可知，她到了山顶，停下来在一个路边的大石头上休息。因此，应选择"stop to do sth. 停下来去做另一件事"。而不仅仅是爬山动作的终止，所以stop doing sth.不正确。

2.forget to do　忘记要去做某事。　(未做)
　forget doing　忘记做过某事。　　(已做)
　The light in the office is stil on. He forgot to turn it off.
　办公室的灯还在亮着，它忘记关了。(没有做关灯的动作)
　He forgot turning the light off.
　他忘记他已经关了灯了。　　　 ( 已做过关灯的动作)
　Don't forget to come tomorrow.
　别忘了明天来。　　　　　　　　 (to come动作未做)

典型例题
　---- The light in the office is still on.
　---- Oh，I forgot___.　　　　　　　　　　
　 A. turning it off　 B. turn it off　 C. to turn it off　 D. having turned it off
　 答案：C。由the light is still on 可知灯亮着，即关灯的动作没有发生，因此用forget to do sth.
而forget doing sth表示灯已经关上了，而自己忘记了这一事实。此处不符合题意。
3.感官动词 see, watch, observe, notice, look at, hear, listen to, smell, taste, feel + do　 表示动作的完整性，真实性；+doing 表示动作的连续性，进行性
　
　I saw him work in the garden yesterday.
　昨天我看见他在花园里干活了。(强调"我看见了"这个事实)
　I saw him working in the garden yesterday.（强调"我见他正干活"这个动作）
　昨天我见他正在花园里干活。

典型例题
1）They knew her very well. They had seen her ___ up from childhood.　
　 A. grow　 B. grew　 C. was growing　 D. to grow
　 答案：A。因题意为，他们看着她长大，因此强调的是成长的过程，而非正在长的动作，因此用see sb do sth 的句型。

2）The missing boy was last seen ___ near the river.　
　A. playing　 B. to be playing　　C. play　　D. to play
　答案A. 本题强调其动作，正在河边玩，应此用see sb. doing sth句型。
4.　begin / start to do sth
　begin / start doing sth.

1)　谈及一项长期活动或开始一种习惯时，使用doing.
　 How old were you when you first started playing the piano?
　 你几岁时开始弹钢琴？
2)　begin, start用进行时时，后面动词用不定式to do
　　I was beginning to get angry。
　　我开始生起气来。
3)　在attempt, intend, begin, start 后接know, understand, realize这类动词时，常用不定式to do。
　　I begin to understand the truth。
　　我开始明白真相。
4)　物作主语时
　mean to do　 打算、想
　mean doing　意味着
　I mean to go, but my father would not allow me to.
　我想去，但是我父亲不肯让我去。
　To raise wage means increasing purchasing power.
　赠加工资意味着增加购买力。
　It began to melt.
5.