最近在进行高三语法总结，讲高中英语里的三大从句：名词性从句，定语从句和状语从句。
我先讲的是名词性从句，因为较其它两类从句，名词性从句更好区分，比较容易理解。
名词性从句由四类构成：主语从句，宾语从句，表语从句和同位语从句。我以主语从句为例，讲讲我以前和今年是怎样讲主语从句的。
Before:
第一步：先举出许多例句：
1）That he will help others is a fact.
2）Whether the meeting will be put off has not been decided yet.
3）Who will do it doesn't matter.
4）Which of the two is better remains to be seen.
5）What he needs are some books.
6）Whatever he said wasn't true.
由这些例句得出结论：that,whether(if),who,whom,which,what,whose,who(ever),whom(ever),which(ever)what(ever)可以引导主语从句。
第二步：再举出例句：
That the earth turns around the sun is known to all.
= It is known to all that the earth turns around the sun.
由这个例句得出结论：that引导的主语从句可以变换成it做形式主语的主语从句。由此引出it做形式主语的几个固定句型，如：
1）It is +n.+that 从句...
It is a pity that...
It is a fact that...
2）It is +adj.+that 从句...
It is possible that...
It is obvious that...
3）It is +不及物动词+that 从句...
It happened that...
It occurred to me that...
4）It is +过去分词+that从句...
It is said that...
It is known to all that...
It is reported that...
It is believed that...
虽然我自己感觉总结的已经很有条理了，但是有的学生还是不能很好的理解主语从句，让我很是郁闷。
李笑来在《人人都能用英语》里写道：一个想法必须足够简单才可能被植入。
我觉得可能自己总结的还是不够简单，所以许多同学还是不能很好的理解主语从句吧。今年讲主语从句时，我再看这些例句，发现一个规律：这些主语从句要不然放在居首，要不然由it做形式主语，判断一个句子是否是主语从句，只需要看是否满足这两个条件其中一个就可以了。
Now：
第一步：只给出两个例句：
1 What you are doing is very difficult.
2 It is certain that you will pass the exam.
第二步：总结规律：
主语从句：句首；形式主语it.
这样讲，学生们遇到句子时，按照这两个标准，就可以很好的判断这个句子是不是主语从句了。
在进行高三语法总复习时，我们教师更要通过大量刷题，总结提炼一些规律性的东西，能用越少的字数总结一个规律最好，字数越少，学生越容易记忆和掌握，拒绝繁复而庞杂的语法讲解。