1.当先行词是everything, anything, nothing (something除外), few, all, none, little, some等代词时，或者被every, any, all, some, no, little, few, much等修饰时，常用that；
All that we have to do is to practise speaking English every day.
Have you taken down everything that Mr. Smith has said?
There seems to be nothing that seems impossible for him in the world.
There is little that I can do for you.
Any woman that/who has a sense of responsibility won’t do such a thing.
The first lesson that I learned will never be forgotten.
This is the best novel that I have seen.
4.当先行词被the very, the only修饰时;
This is the very dictionary that I want to buy.
The only furniture that he had in the room was a bed and a small desk.
Tom is the only person in our school who will attend the meeting.
Who is the man that is standing under the big tree?
Which is the shirt that belongs to me?
They often talked of the things and persons that they remembered in the school.
He is not the man that he was. 他不再是过去那个样子了。
The city is no longer the one that used to be.
She made great progress in English study and won the first prize, which gave us a pleasant surprise.
These books, three of which I have read, are interesting and enjoyable.
The palace to which I often pay a visit was built in the 17th century.
Here is the Advanced English Learning Dictionary which, as I have told you, is a great help to you.
1.先行词为those, one, ones, anyone, people等时;
Those who are from Beijing come this way.
A teacher will come tomorrow who will teach you Japanese.
Is there anybody else who should be invited?
He is a student, as/which is clear from his manner.
She was terrified, as/which I could see from her eyes.
2.as引导非限制性定语从句，可放在主句之前，或者主句之后或者句子中间。另外，as有“正如……”，“正像……”的意思，后边的谓语动词多是see,know, expect, say, mention, report等；which引导的非限制性定语从句只能放在主句之后,意为“这一点”；
As is known to all, water resources are very limited on the earth.
As was expected, he did it successfully.
He is from Hunan Province, as we can see from his accent.
John Dever, as you know, was a famous singer in England.
He has been to Paris more than several times, which I don’t believe.
Kate was always late for school, which made his teacher angry.
3.当先行词被such, the same所修饰时，常用as;
He used such expressions as he could find in the texts.
This is the same book as I lost last week.
She wore the same dress that she wore at Mary’s wedding.
She wore the same dress as her young sister wore.
Mr. Zhang usually criticizes Mary in public, which she doesn’t like at all.
Little Bob always tells a lie, which his parents find strange.
She has been late again, as was expected.
Tom made great progress in Chinese, which made us delighted.
The plane that has just taken off is for London. （定语从句）
The fact that he has been dead is clear. （同位语从句）
2.定语从句由关系代词或者关系副词引导，关系词在从句中充当成分，有时可以省略；同位语从句主要由that引导，在句中一般不作成分，句子也可以由when, where, how, why, whether, what等词引导，充当成分。
The news he told me is true.
The news that he has just died is true.
The problem that we are facing now is how we can collect so much money.
The problem how we can collect so much money is difficult to solve.
3.凡是同位语从句皆可改为The fact/news/idea/order/truth/thought is/was that…结构形式，而定语从句则不可以；
The idea that we could ask the teacher for advice is wonderful.
The idea was that we could ask the teacher for advice.
The fact that the earth moves around the sun is known to all.
The fact is that the earth moves around the sun.