Would you use Should, or should you use would

I have seen many people using should and would interchangeably. Sometimes people use it very confidently to make sure that it does not get noticed :).
But when it comes to the English section in CAT, things may not be so forgiving. So here is a take on the word usage of should and would

Would:
1. Used in conditional sentences: If it weren't so dark, I would have seen the house
2. When converting "will" in a direct sentence to an indirect sentence: He said he would never do it again
3. To say what used to happen: Everyday he would cry remembering her

Should:
1. Most often it is used to mean "ought to": You should not invest in the stock market now
2. Used after 'if' to express hypothetical situations: If it should rain, the match will be cancelled
3. Used after 'that' in expressing suggestions: I suggested that he should leave

Hope it helps. If you have any confusion in using them in any sentence, drop a comment and I shall get back.