首先要搞清楚 定语从句的定义：修饰一个名词或代词,相当于形容词；
引导词：关系代词：that; which; who; whom; whose; as
关系副词：when; where; why
做题技巧：定语从句引导词在从句中一定要充当成分；因此只要分析从句的句子成分,看需要,来确定关系代词或关系副词：即缺少主语或宾语则考虑关系代词,不缺主语或宾语则考虑关系副词.简言之：“做成分,看需要”.如：
I still remember the time _______ we spent together. (that/which)
此句定语从句中spent缺少宾语,故而考虑关系代词.
I still remember the time _______ we met. (when)
此句定语从句中不缺宾语,故而考虑关系副词.
I still remember the first time when I met her.
这句话中when i met her,定语从句用when 引导,与the first 无关,关键是看从句中的成分.
each time, last time, next time,是时间状语连接词,直接引导状语从句,如：
He said he had helped Jane each time he saw her.
他说他每次看见她的时候,都帮助了她.each time 不需 that, 又如：
Next time you come to my city, do drop in on me.
而 This is the first/second...time that sb. have/has done sth. 是固定句型,在讨论现在完成时的语法内应该有.如：
This is the second time that he has been late for class.