以下这个语法点怎样记?（如果死记硬背的话马上就会忘掉）

以下这个语法点怎样记?（如果死记硬背的话马上就会忘掉）
（关于if从句的虚拟语气
1.与过去事实相反,主语是would等+have done,从句是had done
2.与现在事实相反,主语是would等+do,从句是did
3.有将来事实相反,主语是would等+do,从句是did或should+do或were+do
(欢迎高中生或老师解答）
最后一个,were+do改成were+to,我写错了.

答：形式记忆并不难,结合例句记忆更牢固.
列个表格,对记忆有帮助.
　　　　　　　　if 从句谓语 主句谓语
1.现在相反　　　过去式（did）　　　　　　　　　would do
2. 过去相反　　　过过去（had done) would have done
3. 将来相反　　　should do/ were to do/ did would do
注1：.　虚拟条件句的时态就一个字：怪!两个字,奇怪!三个字：不正常!四个字：往过去推!
　现在相反用过去、过去相反过过去、将来相反过将来（should do, be to 也是表将来的,were to　do sth. 也可以这么理解.有时,现在和将来是一个概念,比如：如果我有钱,If I had money, I would do sth. 所以表示与将来情况很可能相反的假设,if 从句也可以用过去式）
注2：主句中的谓语动词时态,先记助动词would+do/ have done,（ 现在和将来是一样的,过去和从句一样,都是完成时态,一个过去完成,一个过去将来完成罢了,只记形式,不记术语）
再扩展知道可以用should, could, might替换would:
　　当主语是第一人称时,可用should代替would, 意思相同,都译作“就会.”,
　　如果有“就能够.”的意思,则用 could 代替　would
如果是”就可能.“的意思,则用might代替　would
注3：If的省略：如果从句中有助动词（包括系动词）were, had, should时,可以通过提前的方式,省去if:
下面是用一些简单基本的句子,来帮助记忆.请将它们背熟了：
1.If I were you, I would try it again.
2.If I had time, I would study French.
3.If you had come yesterday, you would have met him.
4.If it should snow tomorrow, we could ski.
5. Were I to do the work, I should do it some other way.
6. If you had followed my advice, you would be able to finish the work now.
7.But for my brother's help, I would not have finished the work．
如果不是我兄弟帮忙,我就不会完成这项工作.
8. I would have come to see you, but I was too busy yesterday.
注：6为错综时间虚拟条件句.
　　7为隐含条件虚拟语气
　　8为省略条件句（只给出真实情况）的虚拟语气.