Use of should and would

DEFINITION OF SHOULD

Should signifies something you ought to do or something that is a good idea or that something that may happen.

Examples:

• should is use when someone tells you that you ought to go to bed.
• should is use when you believe you must obey the law
• should is use when someone says they will do something if they might happen to win the lottery.

DEFINITION OF WOULD

Would is used to indicate what could potentially happen in the future or when giving advice or when making a request.

Examples

• would is use when you might get a good grade if you study.
• would is use when you ask someone to pass the carrots.
• would is use when you tell someone that your action in rain is to bring an umbrella.

Explanation

• The words should and would are both helping verbs (in particular, modal auxiliaries), but they don't mean the same thing. 
• Should is the past form of the verb shall. Used as an auxiliary, should expresses a condition, an obligation, futurity, or probability.
• Would is the past form of the verb will. Used as an auxiliary, will expresses a possibility, an intention, a desire, a custom, or a request.

Put simply, use should to express an obligation, a necessity, or a prediction; use would to express a wish or a customary action.

Should Sentence Examples

• She should wash them, but there wasn't time.
• It should be ready now.
• Connie should be here any minute.
• So, what should she pack?
• Should he buy candy?
• I should long ago have joined the archduke.
• I should have been with them tonight.
• I should have been checking it.

Would Sentence Examples

• His father hoped that Daniel would grow up to be a wise and famous man.
• One would argue that energy costs will remain high.
• This might be the most difficult decision she would ever make.
• No student of history would argue this point, regardless of his or her politics.
• He would drive them from place to place as his master wished.