归纳起来, do ,does 的用法有四方面：
一、用作一般的动词，均可。do是一不规则变化的动词(do ,did,done)。
do，据人称和单复数的不同而有字形的变化。第一第二人称，以及第一、二、三人称的复数时，都用 do。
第三人称单数时，用 does( he does she does it does )
例如: I do my homework on Sunday.
You do your homework on Sunday.
We do our homework on Sunday.
You do your homework on Sunday.
They do their homeworkon Sunday.
He does his homework on Sunday.
She does her homework on Sunday.
二.当助动词用，用它来构成疑问句.这时它本身没有实义，只是一个构成疑问句的符号而已.这种用法时，它随人称和数的变化规则与上述相同，只是把它放到句子的最前面(句首)。例如：
Do I ...............?
Do you .............?
Do we ..............?
Do you .............?
Do they ............?
Does he ............?
Does she ...........?
Does it ............?
三.当助动词用，与 not 连用使句子构成否定句。其随人称和数的变化规则与上述相同。例如：
I do not ..................? (do not 可简化为 don't ,下同)
You do not ................?
We do not..................?
You do not.................?
They do not................?
He does not................? (does 可简化为 doesn't,下同)
She does not...............?
四.当作助动词,本身在句子中无实义，只是加强句子中动词的语气，其随人称和数的变化同上。例如：
Do write to me.(一定写信给我!)
Never do I see such a fool.(我从来没见过这样的蠢才.)
She does come.(她的确来了.)
按词性，do 还可以用作名词。其意是"欺骗";"宴会,宴请"。例如：
It's all a do.(完全是欺骗.)
We have got a do on to-night.(家里今晚请客.)
