1、主语从句可直接位于主语的位置，如果从句较长，谓语又较短，可用it作形式主语，而将从句放在句末。常见的句型有：

　　It is a facta pitya questiongood news that...

　　It seemsappearshappenedhas turned out that...

　　It is clearimportantlikelypossible that...

　　It is said eportedestimatedhas been proved that...

　　It is said that comic books create a connection between people of the same generation.

　　It seems that the performance is very useful.

　　2、what引导的主语从句表示“...的东西时”，一般不用it作形式主语。

　　What we lack is experience.

　　3、what,who,when,why,whether等词含有各自的疑问意义，但它们引导的主语从句，都用陈述语序。

　　How the plan is to be carried out should be discussed again.

　　I did know why I felt like crying.