1. 我们不知道他是否要在会上发言。
误：We didn’t know whether he is going to speak at the meeting.
正：We didn’t know whether he was going to speak at the meeting.
析：该句主句为过去时，且宾语从句表示从过去某个时间看来将要发生的动作，所以从句要用过去将来时态。
2. 老师问汤姆长大后准备干什么。
误：The teacher asked Tom what he was going to be when he would grow up.
正：The teacher asked Tom what he was going to be when he grew up.
析：在时间状语从句中，常用一般过去时表示在过去看来将要发生的动作。
3. 他们说如果下星期天不下雨他们就去农场。
误：They said that they were going to the farm if it would not rain the next Sunday.
正：They said that they were going to the farm if it didn’t rain the next Sunday.
析：在条件状语从句中，也常用一般过去时表示在过去看来将要发生的动作。
4. 王林打电话告诉她妈妈，她要买一些书。
误：Wang Lin rang up to tell her mother that she should buy some books.
正：Wang Lin rang up to tell her mother that she would buy some books.
析：过去将来时可以由“助动词should/would+动词原形”构成，但should一般只用于第一人称。而would可用于各种人称。
5. 上次我见到你时，你正打算开始乘火车去西藏。
误：Last time I saw you， you had started to go to Tibet by train.
正：Last time I saw you， you were going to start to go to Tibet by train.
析：last time是一般过去时或过去将来时的显著标志。