1.should作助动词主要用于过去将来时，用于第一人称：
I told him that I should see her on Friday.
我告诉他星期五我会见到她。
I thought I should never see you again.
我还以为再也见不到你了。
He hoped that we should support him.
他希望我们支持他。
2.在更多情形下表示“应该”，“应当”，用于各个人称，作用接近情态动词：
What time should we meet?
我们应当在什么时候碰头?
You should do it for your own good.
为了你自己你应该这样做。
She shouldn't leave so soon.
她不应当这么快就走。
should后面有时可用完成或进行形式：
I should have thought of it.
这一点我是应该想到的。(但我没想到。)
They should have told me.
他们应当事前告诉我。(但没这样做。)
You shouldn't be sitting here doing nothing.
你不应当坐在这里什么也不干。
3.用在某些从句中：
He suggested that she should come to Paris.
他建议她到巴黎来。
It will be better that he should be out of France.
他最好离开法国。
I was anxious that our plan should not fail.
我亟盼我们的计划不失败。
4.用在某些从句(甚至主句)中表示惊异、不以为然等情绪：
It's dreadful that they should be so miserable.
真可怕他们竟然这样悲惨。
Why should you talk to me like that?
你怎么竟然和我这样讲话?
It's unfair that this should happen to us.
我们竟然发生这样的事，这是不公平的。
5.用在虚拟条件句中，用于第一人称后(这时用would时更多一些)：
I should never have done it if I hadn't been so hard up.
要不是我处境这般困难我绝不会这样做。
We shouldn't have won without you.
要不是你我们不会获胜。
Should I be free，I will come.
如果我有空我会米的。
6.用在某些句子中使口气显得比较婉转(a)或用来表示揣测(b)：
a.I should like to have a try.
我想试一试。(比I like...更委婉。)
I should think so.
我想是这样的。(比I think...更委婉。)
b.They should be there by now.
现在他们想必己到达。
The book should come out in a month.
这书一个月后估计可出版。
