SHOULD

1. FOR ADVICE, OPINIONS

1.1. We often use should when offering advice or opinions (similar to ought to):

2. FOR OBLIGATION, DUTY, CORRECTNESS

2.1. Another use of should (also similar to ought to) is to indicate a kind of obligation, duty or correctness, often when criticizing another person

3. FOR PROBABILITY, EXPECTATION

3.1. We use should to indicate that we think something is probable (we expect it to happen)

4. FOR CONDITIONALS

4.1. We sometimes use should (instead of would) for the first person singular and plural (I, we) of some conditionals

5. FOR "IF I WERE YOU I SHOULD....."

5.1. We often use the conditional structure "If I were you I should..." to give advice.

6. FOR "WHY SHOULD..?"

6.1. If we don't understand (or agree with) something, we may use Why should..?