有时，不定式跟作主语时一样，可由it来代替，而把不定式放到后面去He makes it a rule to take a walk before breakfast.

I think it interesting to play football while it is snowing hard.

We find it difficult to get everything ready before the time you require.

She cosiders it important to make friends with them.

I don't think it necessary to argue with them on this problem.

有时THERE和TO BE连用表示“有”或“存在(某情况)”等

It is impossible for there to be any more.

Would you like there to be a meeting to discuss the problem?

I expect there to be no argument about this?

有时在个别的介词后可用“疑问词+不定式结构”作其宾语

He has his own decision of how to do it.