主语+would (might, could)+动词原形
1)If it rains tomorrow, our picnic will be put off. (说明：The weather has been very changeable these days.) 条件状语从句的谓语动词用现在时，表示说话人认为下雨的可能性很大。
2)If it rained tomorrow, our picnic would be put off. (说明：The weather has been very good these days.) 条件状语从句的谓语动词用过去时，表示说话人认为下雨的可能性不大。
3)If it should rain tomorrow, our picnic would be put off. (万一明天下雨，我们的野餐就推迟)。条件状语从句的谓语动词用should+动词原形，说明下雨的可能性很小或没有可能，如果下雨，那将是出乎意料的。
4)If it were to rain tomorrow, our picnic would be put off.这句话与上一句意思几乎一模一样。
If I saw him tomorrow, I would pass your note to him.
If she were to miss the train tomorrow, she might come back and start off again the day after tomorrow.
If you should fail, what would you do?
If I were to see her tomorrow, I would tell her the truth.
If it were to rain tomorrow, the meeting would be put off.
I bet Brazil will win the World Cup. If it should lose, I would treat you a meal.
If you had worked hard, you would be very tired. (从句说的是过去，主句指的是现在。)
If he had followed the doctor’s advice, he would be quite all right now.
If I were you, I would have gone home.
Now let’s do some translation:
如果她过去没有刻苦训练的话，就不会跑得这么快。(从句动作指的是过去，主句指的是现在的情况)(Fact: She has trained very hard, so she is able to run very fast now.)
If she hadn’t trained so hard, she wouldn’t be able to run so fast.
如果你当初每天都练习说英语的话，你的英语就会说得很好。(从句动作指的是过去，主句指的是现在的情况) (fact: You didn’t practice speaking English very hard every day, so you can’t speak English very well )