(1)but前面有实义动词do（或其他形式）时，后面的动词不定式不带to；否则，带to。例如：

I can do anything but sing.我就是不会唱歌。

I have no choice but to move.除了搬家，我别无选择。

She wanted nothing but to stay with him. 她只是想和他呆在一起。

(2)在nothing to do之后，动词不定式带不带to均可。

I have nothing to do but (to) wait. 我只好等着，没有别的方法。

There was nothing to do but (to) remain.只能留下来。

(3)在cannot choose but, cannot help but, cannot but后，动词不定式不带to。

She could not choose but leave her children at home.

She could not help but leave her children at home.

She could not but choose to leave her children at home.

她只好把孩子留在家里。