QUICK TIP: Would, could OR should?

What's the difference between would, could and should?  A reader of mine sent in this question, so let's check it out.  Because there are so many aspects to this question, this post will only focus on the past and present tenses of would, could and should.

PAST and PRESENT Tenses

1.  WOULD--WILL (expressing want or one's will to do something)

• Would is the past tense of will.  Often times, would is used in reported speech in the past.
• Ex. "I will go to the swimming pool after work tomorrow."
• Ex. John said that he would go the the swimming pool yesterday.
• Would is also used to express an action that happened regularly in the past.
• Ex. When I was a little girl, I would visit my grandparents in the summer in New York.

2.  COULD--CAN (expressing ability and feasibility)

• Could is the past tense of can.  
• Ex. Today I can surf big waves, but one year ago I couldn't even surf small waves. 
• Ex. He said that he could go to the party, but now he says he can't.

3.  SHOULD HAVE--SHOULD (expressing advice strongly) *Note: There is no past tense of should...there is only should have.

• Should have expresses regret, while should expresses advice.
• Ex. I should have taken an earlier flight because I was late for my business meeting.
• Ex.  You should quit smoking.

Look out for the following post on would have, could have and should have.