WOULD, SHOULD, COULD
Would, should and could are three auxiliary verbs that can be defined as past tenses of will, shall, and can; however, you may learn more from seeing sentences using these auxiliaries than from definitions. Examples of usage follow.
Technically, would is the past tense of will, but it is an auxiliary verb that has many uses, some of which even express the present tense. It can be used in the following ways:
Would you like some coleslaw? = Do you want some coleslaw?
Would you turn in your assignment now? = Please turn in your assignment now.
How would the neighbors react?
What would you do if I sang out of tune?
In the two sentences above, would means about the same thing as will.
I would like more coleslaw, please. = I want more coleslaw, please.
I would like you to sit down now. = I want you to sit down now.
I would have helped you if I had known you were stranded.
(I didn't know that you were stranded. This "not knowing" occurred before my not helping you.)
John would've missed the trail if Mary hadn't waited for him at the stream.
(First Mary waited for him. If her response had been to not wait, then next John would have been on the wrong trail.)
I would have to say that you're acting a bit immature.
Here would has a similar meaning to do but less emphatic.
Should I win a million dollars, I would fix up my house.
Think of should as if, and would as will.
Helen would sob whenever John would leave home.
Think of would as did.
For a moment the plane would be airborne, then it would bump back down along the hard earth.
(The plane was in the air and then back on the ground several times.)
I would sooner die than face them. = I prefer death in place of facing them.
I would rather handwrite than type. = I prefer handwriting instead in typing.
However, the second choice may by implied but not stated:
I would rather die.
Implied is that I would rather die than...do whatever it is that the context has provided as an alternative to dying.
Those people would allow gambling. = Those people want to allow gambling.
Would it were so. = I wish it were so. (Infrequently used)
We wish that he would go. = We want him to go.
She said she would come. = She said she was planning to come.
I would put off the test if I could.
This means my choice is to delay taking the test, but I do not have the ability to delay taking it.
The answer would seem to be correct. = The answer is probably correct.
He calculated that he would get to the camp around 6 p.m. The men would have dinner ready for him.
The first sentence means he believed his camp arrival time was going to be about 6:00 p.m. The "calculating" (or believing) happened in the past, yet the arrival is going to occur later. The second sentence predicts that, at that future time, dinner will be ready for him.
Would you had changed your mind. = I wish you had changed your mind.
Would you have changed your mind. = If circumstances had been different, is it possible that you might have changed your mind?
Technically, should is the past tense of shall, but it is an auxiliary verb with a few uses, not all of which are in the past tense, namely, the following:
Should you have erased the disk? = Were you supposed to have erased it?
Should I turn in my assignment now? = Am I supposed to turn in my assignment now?
Here, should means about the same thing as ought.
You should floss and brush your teeth after every meal.
Think of should as supposed to, as in the previous example, but here to make a persuasive statement.
If I should find your coat, I will be sure to call you.
Think of should as do; furthermore, should could be left out of the above sentence, leaving, "If I find your coat, I will be sure to call you." Alternately, if could be left out of the sentence: "Should I find your coat, I will be sure to call you."
Should you wish to do so, you may have hot tea and biscuits. = If you wish to do so, you may have hot tea and biscuits.
With an early start, they should be here by noon.
Think of should as ought to or probably will.
I should like to go home now. = I want to go home now.
I should think that a healthy forest program is essential to any presidential victory.= I think that a healthy forest program is essential to any presidential victory.
Technically, could is the past tense of can, but it is an auxiliary verb with a few uses, not all of which are in the past tense, namely the following:
In those days, all the people could build houses. = In those days, all the people had the ability to build houses.
Could you have erased the disk? = Is it possible that you erased the disk?
Could I leave now? = May I leave now; am I allowed to leave now?
You could study harder than you do. = You have the potential to study harder than you do.
He knew the sunset could be spectacular. = He knew that the sunset was sometimes spectacular.
I could be wrong. = I may be wrong.
Could you come over here, please? = Please come here.
In conclusion, you could use these three auxiliaries if you would, and you should! Write a sample sentence for each possible usage of could, would, and should; then ask any Reading/Writing or English tutor for further assistance.