WOULD
Wish — I would like to see that movie.
Refusal — He wouldn’t disclose anything.
Determination — He would have his own battle.
Past habit — He would play tennis for hours.
Willingness (in the past) — He said that he would go with me.
Polite speech — Would you mind repeating the for me?
Uncertainty — Had we met, I would have told her everything.
COULD
Possibility — He could be the one who stole the purse.
Past ability — I could run for kilometres when I was a kid.
Suggestion — You could spend your vacation in Roma.
Conditional — If I had more money, I could travel around the world.
Polite request — Could I borrow your car ?
SHOULD
Duty or Obligation — We should help smaller countries.
Advice — You shouldn’t work so little.
Supposition, Possibility, Condition — If it should rain, the station will remain closed.
WOULD HAVE, SHOULD HAVE, COULD HAVE
To talk about things that didn’t really happen in the past.
Could have + past participle — Something was possible in the past, or you had the ability to do something in the past, but you didn’t do it.
Example:
I could have worked till late, but I decided to sleep early.
Should have + past participle
Something that would have been a good idea but you didn’t do it or something that we think has already happened, but we’re not certain about it.
Examples:
I should have studied a few more hours.
My friend should have arrived by now.
Would have + past participle
Used in past conditionals to talk about something that did not happen.
Example:
If it would have been closer, we would have gone for a day.
