Get or take

In this situation the best will be:
"Coud you take a plate for me?" - It means that you ask someone to do it for you.
And if you say:
"Can you get a plate for me?" - You ask if it is possible to find there any plates. You don't know if they are here.

Thanks for your explanation.

But I just found out an explanation about "take" and "get" from About.com.

It says, " If the speaker refers to something that is at her current location, she uses bring. Generally, use bring when something moves from there to here. When speaking about going somewhere and getting something and then bringing it back, use get

Once again:

You're at home, you have already made a pumpkin pie, you call your friend, you invite him and you say "could you bring a plate?". Because you don't have any.

The same situation, but you and your friend are going to meet in the park, so you say "coud you take a plate(with you) for me?"

And finally you meet your friend in the park, but he doesn't

I think, Take, is the right verb

Wenwen"I'm making a pumpkin pie. Can you take/get a plate for me?" Which verb is suitable?

Which is suitable depends on what you want the other person to do.

If you want the other person to take a plate for you, use 'take'.
If you want the other person to get a plate for you, use 'get'.

Also, your first sentence doesn't have much relationshi