一。to 是介词而不是不定式标志时后面的动词要加ing。如 : 
in addition to doing除做此之外 
look forward to doing 渴望做某事 
pay attention to doing注意做 
make a contribution to doing为。
  。。作贡献 
二。1。很多都是不定式做宾语的情况。 
常见的有want,like,hope,wish,hate,manage,ask,promise,pretend,decide,happen。plan,etc。+to do。另外tell,advise,find out,show。
  know。teach,decide,learn,wonder等动词后常用一个带连接代词或连接副词的不定式做宾语。如: 
He didn't know what to do。他不知如何是好。 
2。还有不定式做表语的情况 
Her wish is to become a doctor。
  他的愿望是成为一名医生。 
3。做定语的情况 
I want to get something to eat。我想找些吃的东西。 
4。做状语 
He ran over to welcome the guest。他跑过去欢迎客人到来。
   
What have I said to make you so excited?我说了什么让你这么兴奋? 
5。在复合结构中的不定式 
want, ask,tell,invite,force,get,beg,allow,wish,would like,expect,advise,order,cause,encourage等动词后跟不定式做宾补。
   
Would you like us to go with you ? 
6。以be said/reported/known,seem,happen,prove,appear,be likely/certain/sure等结构和不定式一起构成谓语。
   
They are likely to be on the farm now。他们现在可能已经在农场上了。 
。