关于虚拟语气问题

鉴别虚拟语气主要看的是时态.
与现在事实相反，从句用一般过去时，其中be动词统一用were，主句用would或was/were going to加动词原形，也就是过去将来时。比如，if I were you, i would not agree with it.
与过去事实相反，从句用过去完成时，主句用would或was/were going to加完成时，也就是过去将来完成时。比如，if he had accepted my advice, he would not have failed the exam_
与将来事实相反时，条件从句的时态为一般过去时/（were+不定式）/（should+动词原形），比如，if you succeeded, I would give you a surprise.
与现在事实相反和将来事实相反的时态是很相近的，要看意思。
if...will...是条件状语从句，是可能发生，if后面用现在时态表示将来。

详细一点。。