Question

Please tell me how can we use should be, could be, would be & what is the difference between this words.

Answer 1

Should be is ADVICE. Could be is possible. Would be is  a dream. You should be more careful. You could be rich if you worked hard. It would be amazing to be able to fly

Answer 2

What grstrad said is completely right. One more thing to add on. Use should be when you are saying that someone is supposed to happen. For example, "My keys should be right here." In that sentence you are saying that the keys are supposed to be there.