Should

 Used as an auxiliary verb, to express a conditional or contingent act or state, or as a supposition of an actual fact; also, to express moral obligation (see Shall); e. g.: they should have come last week; if I should go; I should think you could go. ``You have done that you should be sorry for.''That is to say, "Should" is most commonly used to make recommendations or give advice. It can also be used to express obligation as well as expectation.

Examples:

• When you go to Berlin, you should visit the palaces in Potsdam. recommendation
• You should focus more on your family and less on work. advice
• I really should be in the office by 7:00 AM. obligation
• By now, they should already be in Dubai. expectation

Using "Should" in Present, Past, and Future

Most modal verbs behave quite irregularly in the past and the future. Study the chart below to learn how "should" behaves in different contexts.

Modal Use	Positive Forms 1. = Present   2. = Past   3. = Future	Negative Forms 1. = Present   2. = Past   3. = Future	You can also use:
should recommendation, advisability	1. People with high cholesterol should eat low-fat foods. 2. Frank should have eaten low-fat foods. That might have prevented his heart attack. 3. You really should start eating better.	1. Sarah shouldn't smoke so much. It's not good for her health. 2. Sarah shouldn't have smoked so much. That's what caused her health problems. 3. Sarah shouldn't smoke when she visits Martha next week. Martha hates when people smoke in her house.	ought to
should obligation	I should be at work before 9:00. We should return the video before the video rental store closes. "Should" can also express something between recommendation and obligation. "Be supposed to" expresses a similar idea and can easily be used in the past or in negative forms.	NO NEGATIVE FORMS	be supposed to
should expectation	1. Susan should be in New York by now.  2. Susan should have arrived in New York last week. Let's call her and see what she is up to. 3. Susan should be in New York by next week. Her new job starts on Monday.	1. Susan shouldn't be in New York yet. 2. Susan shouldn't have arrived in New York until yesterday. 3. Susan shouldn't arrive in New York until next week.	ought to, be supposed to