should 
/ˈʃʊd, ʃəd/ verb
past tense of shall /ˈʃʊd, ʃəd/ verb [modal verb] 1 a — used to say or suggest that something is the proper, reasonable, or best thing to do ▪ You should [=ought to] get some rest. ▪ They should be punished. ▪ We should leave a few minutes early to make sure we get there on time. ▪ Maybe you should consider finding a new job. ▪ I should emphasize that these numbers are only estimates. ▪ My friends say that I should quit the team. ▪ What time should we meet? [=what is the best time for us to meet?; what time do you want to meet?] ▪ Patients should inform the receptionist upon their arrival.
b — used with have to say that something was the proper, reasonable, or best thing to do but was not done ▪ You should have been more careful. ▪ She shouldn't have spoken to him so rudely. ▪ What should I have done? ▪ Should I not have gone? [=was it wrong for me to go?] ▪ I should have known that he would be late. [=I didn't know that he would be late, but it would have been reasonable for me to expect it because he is often late]
c — used with have to say that you wish someone had seen, heard, or experienced something ▪ You should have seen her face [=I wish that you had seen her face] when she opened the present. ▪ It was so funny. You should have been there. 2 — used to ask for someone's opinion ▪ Should [=(more formally) shall] I turn the music down? ▪ What should we have for lunch? 3 — used to say that something is expected or correct ▪ Everyone should [=ought to] have a copy of the handout. ▪ There should be four place settings at the table, not six. ▪ “He feels very sorry about what happened.” “Well, he should!” ▪ You should be ashamed of yourself, behaving so rudely to our guests! ▪ They should be here by now. = They should have arrived by now. [=I expected them to be here by now] 4 a — used when saying that you feel a specified way about someone's words or behavior ▪ I'm surprised that he should intentionally be so rude to you. ▪ It's strange (that) you should say that. ▪ Funny you should mention it. [=I think it's odd/strange that you mentioned it] I've been thinking the same thing.
b — used to emphasize what you believe, think, hope, etc. ▪ I should imagine it won't take more than two hours to drive there. [=I am fairly certain that it won't take more than two hours] ▪ I should think not. [=I really don't think so] ▪ I should hope that she would apologize. [=I expect her to apologize] ▪ “She apologized for her rude behavior.” “Well, I should hope so!” 5 — used with have in negative statements as a polite way of thanking someone for doing something ▪ You really should not have gone to all that trouble on my account—but I'm glad you did! ▪ Flowers for me? You shouldn't have. 6 somewhat formal — used to talk about the result or effect of something that may happen or be true ▪ Should [=if] you change your mind, please let us know. ▪ I will feel very guilty should anything go wrong. [=if anything goes wrong] — usually used with if ▪ I will feel very guilty if anything should [=were to] go wrong. ▪ If he should call [=if he calls], tell him I'm not home. ▪ If you should see them [=if you see them], say hello for me. 7 Brit — used to say that you would do or feel something if something specified happened — only used after I or we ▪ If my husband treated me like that, I should [=would] divorce him. ▪ I should be surprised if many people go to the fair on such a rainy day. ▪ I should not be surprised if no one goes. ▪ I shouldn't [=wouldn't] be surprised at all. 8 Brit — used when giving someone advice — only used after I or we ▪ I should [=would] see a doctor if I were you. 9 Brit — used to say that you want to do or want to have something — only used after I or we ▪ “They really need some help.” “Well, I should be glad to help them.” ▪ I should like to call my lawyer. ▪ “Would you care for a drink?” “I should like one very much.”
b — used with have to say that something was the proper, reasonable, or best thing to do but was not done ▪ You should have been more careful. ▪ She shouldn't have spoken to him so rudely. ▪ What should I have done? ▪ Should I not have gone? [=was it wrong for me to go?] ▪ I should have known that he would be late. [=I didn't know that he would be late, but it would have been reasonable for me to expect it because he is often late]
c — used with have to say that you wish someone had seen, heard, or experienced something ▪ You should have seen her face [=I wish that you had seen her face] when she opened the present. ▪ It was so funny. You should have been there.
b — used to emphasize what you believe, think, hope, etc. ▪ I should imagine it won't take more than two hours to drive there. [=I am fairly certain that it won't take more than two hours] ▪ I should think not. [=I really don't think so] ▪ I should hope that she would apologize. [=I expect her to apologize] ▪ “She apologized for her rude behavior.” “Well, I should hope so!”
how/why should I/we know
— used to say that you do not know the answer to a question and are surprised that you were asked it ▪ “Where did they go?” “How should I know?”
what/who should you see but
— used to say that you are surprised to see something or someone ▪ I looked up and what should I see but a hummingbird hovering over my head. ▪ They were walking along when who should they see but Kim!
