I wish I could fly.
I wish I were her.
I wish I did homework.
②表示过去不能实现的愿望，从句谓语用had done或could/should have done.
I wish I had studied harder then.=I wish I could/should have studied harder then.
I wish I had not eaten so much for lunch.=I wish I could/should not eaten so much for lunch.
He wishes I had not told him the truth.=He wishes I could/should not have told him the truth.
I wish he would invite me to the party this Sunday.
Some people wish they would never die.
4. 用在if only （要是……就好了）引导的从句中.
与过去事实相反 had done或could/should have done.
与将来事实相反 would/could/might do
如：If only I were a boy.
If only I hadn’t been that nervous the other day.
Her best friend Amy is dead. If only Amy could attend her wedding, she would be very happy.
注; if only 和only if的区别
如; You can make progress only if you work hard.
I will trust him again only if he turns over a new leaf.
5. 在 “as if/ as though”(仿佛，好像) 引导的状语从句中
与过去事实相反 had done
与将来事实相反 would/could/might do
如： Don’t look at me like that.as though I were a murderer.
He acted as if he had not done it. But everyone knew he did it.
注：若as if/as though从句表示的是真实情况，则不用虚拟语气，正常用陈述语气。
如：It seems as if you know each other.
Look at those black clouds. It looks as if it’s going to rain.
6. would rather(宁愿，宁可), would sooner(宁愿), would just as soon(宁愿)引导的宾语从句中
① 表示现在或将来的虚拟 did/were
如：She is a great teacher. I would rather she were my teacher.
I would rather you came next week instead of today.
② 表示过去的虚拟 had done
如；I would rather that I hadn’t joined the club.
He would rather that you hadn’t told him the truth.
7. 用在It is (about/high)time+ that从句中(that可省略)，表示应该做，但还没做,可译为“（早）该做某事了”。
如：It’s high time we went/should go to bed.
It’s about time that you washed/should wash your car
“一个坚持(insist)、两个命令(order, command)、四个建议(advise, suggest, propose，recommend)、四个要求(demand, require, request, desire)”
should +do, should可省略
如: He insisted that I (should) go with him.
He ordered that it (should) be sent back.
The doctor advises /suggested/proposed/ that people (should) not smoke.
She requires /demands/requests that I (should) appear.
由上述动词派生或转化来的名词形式，如suggestion, proposal, recommendation, demand, order, desire, request, requirement, insistence, advice, decision等词引导的同位语从句或表语从句中也要用相应的虚拟语气.
如：He ordered that all the books (should) be sent at once.（宾语从句）
= His order was that all the books (should) be sent at once. (表语从句)
= He gave the order that all the books (should) be sent at once. (同位语从句)
I propose that he (should) be chosen as our boss. (宾语从句)
= My propose was that he should be chosen as our boss.(表语从句)
He suggested that we (should) not give up. (宾语从句)
=His suggestion was that we (should) not give up. (表语从句)
=He made a suggestion that we (should) not give up. (同位语从句)
The teacher demanded that all the students (should) hand in their homework.(宾语从句)
= The teacher's demand was that all the students should hand in their homework.（表语从句）
The doctor insisted that he (should) not eat too much meat. (宾语从句)
=The doctor’s insistence was that he (should) not eat too much meat. (表语从句)
注; suggest 和insist
1) Suggest 表示“表明，暗示”的意思时，要用陈述语气。
如： Her face suggested that she was ill, so her mother suggested that she (should) be sent to hospital.
2) insist 表示“坚持说，坚持认为”的意思时，要用陈述语气。
如： The thief insisted that he hadn’t stolen the wallet, and he insisted that he (should) not be caught.
9. 在It is + 某些形容词/名词 + that 从句的句型中,that从句中的谓语动词常用虚拟语气,即 “(should) + do” ，表达说话人的要求,命令，责备, 强调，遗憾等语气。
这些词主要有:important, necessary（必要的）, essential（关键的，及其重要的）, imperative（必需的）, natural, strange, advisable（可取的，明智的）, desirable（可取的）, impossible, possible, probable（很可能的）, astonishing（令人震惊的）, surprising,
suggested（被建议的）, requested,（被要求的） recommended（被推荐的）, ordered, proposed, ,no wonder(怪不得)，a shame（可惜，遗憾, a pity(可惜，遗憾)等.
如：It is necessary/essential/imperative/important that he should be given the chance.
It's ordered that he should come back without delay.
It's very essential that we should learn more knowledge.
It's advisable that he should take part in the party.
It was suggested that the sports meeting be put off.
It is a shame that he (should) miss his favorite star.
It is a pity that he should be so careless.
10. 由for fear that(生怕，唯恐), in case（以防，以免）, lest（以防）引导的状语从句中,用 “ (should) + do” 表示 “惟恐，防备，推测”的意思. should可以省略。
如: Keep quiet in case you （should） wake up the baby.
He walked out of the room quietly lest his mother (should) notice him.
11. 当句子中带有介词如but, but for, or, without，otherwise表示“要不是”，“否则”的意思时，相当于if 引导的条件句，要用虚拟语气。
But for your advice, I could not have done it so successfully.
=If you hadn’t given me your advice, I could not have done it so successfully.
Without electricity, we would live a boring life.
=If there were no electricity, we would live a boring life.
I am busy now, or/otherwise I would help you.
=If I were not busy now, I would help you.