方法一：当主句谓语动词是hope， decide， wish， choose， agree， promise等，且宾语从句的主语与主句主语一致时，宾语从句可简化为不定式结构。例如：
Li Ming hopes he will be back very soon. →Li Ming hopes to be back very soon.
We decided that we would help him. →We decided to help him.
方法二：当主句谓语动词是know， learn， remember， forget， tell等动词，且主句主语与从句主语一致时，宾语从句可简化为“疑问词+不定式”结构。例如：
She has forgotten how she can open the window. →She has forgotten how to open the window.
注：当主句谓语动词是tell， ask， show， teach等动词，且后带双宾语，从句主语和间接宾语一致时，宾语从句可简化为“疑问词+不定式”结构。例如：
Could you tell me how I can get to the station？ →Could you tell me how to get to the station？
The headmaster ordered that we should start at once. → The headmaster ordered us to start at once.
He insisted that he should go with us. →He insisted on going with us.
The poor boy doesn't know when and where he was born. →The poor boy doesn't know the time and the place of his birth.
Liu Ping found that there was a wallet lying on the ground. → Liu Ping found a wallet lying on the ground.
It seemed that the boys were going to win. →The boys seemed to win.
I found that it was difficult to learn English well. →I found it difficult to learn English well.
Soon we found that the ground was covered with thick snow. →Soon we found the ground covered with thick snow.
They found that the box was very heavy. →They found the box very heavy.