1、看句中有無be動詞，如有，直接在be動詞后+not。2、看句中有無情態(tài)動詞，如有，直接在情態(tài)動詞后+not。3、如上述二者都沒有，就應用助動詞+not。4、原句中動詞假如發(fā)生變化就要恢復成原形。

一、有be動詞(am、is、are)和情態(tài)動詞(can、could、may、must、shoud、will、would等)時，直接在be動詞和情態(tài)動詞后面加not，some變?yōu)閍ny，and變?yōu)閛r，too變?yōu)閑ither，其他的照抄。

例如:

①、I am a student. – I am not a student.

②、Amy is a good girl.–Amy is nota good girl.

③、These flowers are very beautiful.–These flowersare not very beautiful.

④、I can swim.–Ican't(can not)swim.

⑤、There are some books on the table.–There are not anybooks on the table.

⑥、Jack is a doctor , too.–Jack is not a doctor , either.

⑦、I was a student ten years ago.–I was nota student ten years ago.

注:⑴、 some 、and 用于肯定句中，any、or用于否定句和疑問句中。

⑵、was是is和are的過去式，were是are的過去式。

二、沒有be動詞(am、is、are)和情態(tài)動詞(can、could、may、must、shoud、will、would等)時，在動詞前面加don't、doesn't、didn't，動詞恢復成原型，some變?yōu)閍ny，and變?yōu)閛r，too變?yōu)閑ither，其他的照抄。

例如:

①、I like math.–I don't likemath.

②、Jack likes math, too.–Jack doesn't like math , either.

③、They like bananas and apples.–They don't like bananas orapples.

④、Lily gets up at six every morning.–Lily doesn't getup at six every morning.

⑤、His father likes playing football.–His father doesn't likeplaying football.

⑥、I went fishing yesterday.–l didn't gofishing yesterday.

注:⑴、當句子是一般過去時態(tài)時，在動詞前加didn't，動詞恢復成原型。

⑵、當句子是一般現在時態(tài)時，主語是第三人稱單數時，在動詞前加doesn't，動詞恢復成原型;主語不是第三人稱單數時，在動詞前加don't。