1.在一般现在时和一般过去时中,1)在be后加not.
He is here.否定：He isn't here They were very happy.否定：They weren't very happy
如动词是其它的实意动词：
2)如是动词原形则在前加助动词do 再加not；
They do sports every day.(do在这里是“做”的意思,是实意动词,不能直接加not否定)
否定：They don't do sports every day.
3）动词是第三人称单数则在前加助动词does 再加not； ,且单三还原成原形
He gets up at six.否定：He doesn't get up at six
4)动词是过去式,则在前加助动词did再加not；
We visited the old man yesterday.否定：We didn't visit the old man yesterday.
2.如果谓语动词是情态动词,则在情态动词后加not.情态动词也是一种助动词
We can dance very well.否定：We can't dance very well
3.如果谓语动词是其它时态,则在第一个助动词后加not
They are working hard.(be dong 中的be帮助构成了时态,是助动词)
否定：They are not working hard.
He has finished his homework.(have done 中的have帮助构成了时态,也是助动词)
否定：He has not finished his homework.
4.使用no,hardly,seldom,never,nobody,few,little 等否定词
Nobody is in the room.=There is not anybody in the room.