助动词的用法问题可分析如下：
1.be
（1）构成进行时态
Some boys are playing on the grass.一些男孩正在草地上玩。（现在进行时）
Yesterday we were discussing a new teaching plan.
昨天我们在讨论新教学计划。（过去进行时）
（2）构成被动语态
The door was broken by Tom.门是汤姆打破的。
English is taught in our school.我校教英语。
（3）be+动词不定式
The prize was to honour him for his great discoveries.
这项奖励是为了对他的重大发现而表示的敬意。（表示目的）
The president is to visit China next year.
总统将于明年访问中国。（表示按计划安排要发生的事情）
You are not to bring any mobile communication means into the exam-room.
任何移动通讯工具都不得带入考场。（表示命令，指令）
This letter is to be handed to him in person.
这封信必须要面交他本人。（表示必须，必要）
2.have
（1）构成各种完成时态
He has left for Japan.他已去了日本。（现在完成时）
I have been reading a novel since this morning.
从今早起，我就一直在看一本小说。（现在完成进行时）
He had finished it when I arrived.我到达的时候他已完成了。（过去完成时）
He will have finished it when we arrive.当我们到达时他将完成了。（将来完成时）
（2）构成被动语态
The important problem has been discussed for nearly two weeks.
那个重要的问题已经被讨论近两个星期了。
How long has the machine been used？ 这机器使用有多久了？
Every means has been used to get him to change his mind.
为了转变他的想法，所有的办法都用过了。
（3）口语中，常用have got代替have
I only like films that have got plenty of action.
我只喜欢有很多惊险动作的电影。
We have simply got to see him.我们非见他不可。
3.do
（1）构成疑问句
Do you go to school on Saturday？ 你星期六上学吗？
Does he like swimming in summer？ 他夏天喜欢游泳吗？
Did you take breakfast yesterday？ 你昨天吃早饭了吗？
（2）构成否定句
You don’t study hard.你不用功。
She doesn’t enjoy reading.她不喜欢阅读。
I didn’t sleep well last night.我昨夜睡得不好。
（3）构成否定的祈使句
Don’t be so careless.不要那么粗心大意。
Don’t hesitate to come when you need help.有困难只管来找我。
（4）强调谓语
I do wish you will come.我实在希望你会来。
They did go there.他们的确去了那里。
Do tell me the truth.一定要告诉我事实。
（5）代替实义动词
— Does he also study geography？ 他也学地理吗？
— Yes，he does.是的，他学地理。（does代替studies）
He works even harder than you do.他比你还要用功。（do代替work）
4.shall，will
（1）shall和will构成一般将来时。
I shall study harder at English.我将更加努力地学习英语。
I shall not come if it rains tomorrow.如果明天下雨，我就不来。
My brother will leave for the United States next week.
我的哥哥下星期要到美国去。
He will go to Shanghai.他要去上海。
（2）shall只用于第一人称，will可用于第一、第二、第三人称。
I will help him if he asks me.只要他愿意，我会帮助他。
You will report me afterwards.事后你必须向我报告。
They say that it will rain tomorrow.他们说明天下雨。