Take a look at these useful expressions:

If you require some information you can say:

-Could you tell me if/when/how much/why...?
-I wonder if you could tell me...?
-I'd like to know...
-I'd like some information about...

Or you can write:

We require the following information...
Please let us know whether/when/how much...

When someone gives you some information, you can reply:

-Oh, I see.
-That's interesting.
-Really?
-Thanks for letting me know.

If somesone asks you for information, you can reply:

-As far as I know, ...
-Well, in confidence, I can tell you that...

-I'm afraid I don't know.
-I've no idea, I'm afraid.
-I don't have that information available just now. Can I call you back?
-I'm not sure, I'll have to find out. Can I let you know tomorrow?
-I'm afraid I can't tell you that - it's confidential.

If you want to give someone some information you can say:

-I'd like you to know that...
-I think you should know that...
-Did you know that...?

Or you can write:

We should like to inform you that...
Here is the information you required...

If someone hasn't given you enough information you can say:

-Could you tell me some more about...?
-I'd like some more information about...
-I'd also like to know...
-When/How much/Why exactly...?
-There's something else I'd like to know...
-Can you give me some more details about...?