Requests are used when you want someone to do something for you.  The modals can, could, will and would are used as in the following examples.  There is no difference between them, which means that you can use any of these words and it’s the same.  Please can be added to make your request more polite but is not necessary.

Can you, Can I:

Can you tell me when the store closes?
Can you please help me find my dog?

Can I borrow $20, please?
Can I see some identification, please?

Could you, Could I:

Could you give me your email address?
Could you tell me the time, please?

Could I get a ride home, please?
Could I meet with you tomorrow afternoon?

Will you:

Will you give me a ride downtown, please?
Will you please pass me the salt?

Would you:

Would you please stop making all that noise?
Would you sit down here next to me?

(Notice that the verb after all these modals is in the simple form.)

Here are other ways you can make a request:

Would you mind:

Would you mind closing the door on your way out?
Would you mind turning down the music a little?
(Notice that the verb after would you mind is a gerund (-ing))

I would like:

I would like you to join me for dinner.
I would like another cup of tea, please.
NOT:  I want another cup of tea, please. (This is a little impolite)

I’d (really) appreciate it if you can / could / will / would.

Really is optional.

I’d really appreciate it if you can lend me a little money until payday.
I’d appreciate it if you could let me use your car this Friday.
I’d really appreciate it if you will wait for me.
I would appreciate it if you wouldn’t text me all the time.

You can also drop the modal, but you must put the following verb in the simple past tense.

I’d appreciate it if you dropped me off downtown.
I would appreciate it if you waited for me outside.

When asking for or giving permission, 3 modal verbs are used: can, could and may.  Although many people think that may is more polite than the other 2, all 3 are equally polite, especially if you add please.  You can ask for permission either for yourself or for someone else.  Remember that the verb after these modals is always in the simple form.

Examples:
Can I please use your washroom?
Can my friend get a free sample too, please?

Could I just get my money back, please?
Could my child please stay here until I get back?

May I please have another slice of cake?
May my mother have this seat, please?

(Notice that please can go either before the simple form verb or at the end of the sentence.)

Negative permission is called prohibition.  Use can and may in the negative to indicate that someone doesn’t have permission.

Examples:
You can’t park your car in my neighbor’s driveway.
Your friend cannot stay here overnight.

BUT NOT:  You could not smoke in this room. (which is past ability, not prohibition)

You may not leave class early.
Your dog may not lie on the sofa.
(Note:  You cannot contract may not (mayn’t.))

Besides these 3 modals you can also ask permission with Is it alright/okay (with you) if …, Do you mind if…, and Would you mind if…. 

With Is it alright/okay (with you) if and Do you mind if… always use the present simple form of the verb.

Examples:
Is it alright if my friend comes with us?
Is it okay with you if I don’t stay long?

Do you mind if I close the window?
Do you mind if I sit down?

After Would you mind if…, you can use the present simple or the past simple tense, and there’s no difference in meaning.

Examples:
Would you mind if I get something to eat?
Would you mind if I got something to eat?

Would you mind if I leave early?
Would you mind if I left early?

NOTE: To give permission when someone uses the expressions Do you mind if… and Would you mind if…, say, “No, not at all,” or “No, go ahead.”  Without these extra words after “No,” the listener may think you’re not giving permission.  If you don’t want to give permission, don’t just say “Yes,” but say “Yes I do” or “Yes I would.”

Conversation:

Brian:  Is it alright if I leave early today?  I have a job interview this afternoon.

Teacher:  Sure.  No problem.  Just remember to do your homework for tomorrow.

Brian:  Could I do it on the weekend.  I have a test in math tomorrow and I have to study.

Teacher:  You can’t skip your homework in this class.  Without practice you won’t learn as well.

Brian:  I understand, but I’ve really got a lot to do tonight.   Would you mind if I skip it this once?

Teacher:  No, not at all.  I guess one time won’t hurt.

Brian:  Thanks.

© 2013 Ambien Malecot