一、有的固定动词后面既可以接动词不定式或动名词，充当宾语的成分，但其表达的意思非常的不同。

mean to do想要(做某事) propose to do 打算(做某事)

mean doing意味(做某事) propose doing建议(做某事)

forget to do忘记(要做的事) remember to do记得(要做某事)

forget doing忘记(已做的事) remember doing记得(已做过的事)

go on to do继而(做另一件事) stop to do停下来去做另一件事

go on doing继续(做原来的事) stop doing停止正在做的事

比如：I remember to deal with this urgent issue tomorrow.

I remember sending you a postcard last Christmas.

二、不定式的习惯用法，即他们之间形成一个固定的搭配。

这样有两种大的情形：

1,cannot help but do cannot but do

cannot choose but do can do nothing but do

have no choice/alternative but to do

上述句型的意思接近，即“不得不做”、“不禁做”、“不由自主地做”、“不能不做”、“只能做”。其共同的特点是都有一个否定词和but。

比如：I have no choice but to abide by what you have told me.

2,be busy/active doing sth. have difficulty/trouble/problem doing sth.

It’s no good/use/picnic doing sth. have a good/great/wonderful time doing sth.

spend/waste time doing sth. There is no point/sense/harm/ use doing sth.

cannot help doing sth.

比如： I can not help crying at the sight of the touching movie,

There is no point in talking about non-sense like that,

I have difficulty in passing the exam without your great help.