I am overloaded with e-mails, mainly from 10-12 staff members in my
section in my company.  Often too long and not focused.  And many c.c.
-copies to me without indication of why I get them and whether I need
to take action or whether for info etc....

I wish to give them some advise or even set some rules. Could you
possibly trace some existing guidelines on e-mail etiquette ?

For a long list of general do's and don'ts, I found this helpful piece
on Dynamo.com:  (Following this list are some sites for keeping emails
shorter and to the point)

The following tips should help you avoid some of the pitfalls. 

Good Email Etiquette
Do check to see what your organisation's email policy is. Many
organisations have rules about the types of message that can be sent
and also if your email is monitored or screened.
Do try to think about the message content before you send it out.   
Do make sure that the content is relevant to the recipients. Nobody
likes to receive junk email.
Do be polite. Terseness can be misinterpreted. 
Do trim any quoted message down as much as possible. 
Do ensure that you have a relevant "Subject" line. 
Do try to quote from the original message where relevant. You can
break the quoted message down into paragraphs and comment on them
individually to make it clearer.
Do be patient, especially with inexperienced email users. Give people
the benefit of the doubt - just because you are familiar with email
etiquette, it doesn't mean that they are.
Do include a brief signature on your email messages to help the
recipient understand who it is from, especially if you are dealing
with someone you do not know very well.
Do remember to tell people the format of any attachments you send if
they're anything other than basic Microsoft Office file types.
Do tell your correspondent if you forward a message to somebody else
to deal with, so they know who to expect a reply from.

Bad Email Etiquette
Don't reply to an email message when angry , as you may regret it
later. Once the message has been sent, you will not be able to recover
it.
Don't copy out an entire, long message just to add a line or two of
text such as "I agree".
Don't type in CAPITALS as this is considered to be SHOUTING. This is
one of the rudest things you can do.
Don't over-use punctuation such as exclamation marks ("!") as these
are meant to be for emphasis. In particular avoid more than one
exclamation mark ("!!"), especially if your email is quite formal.
Also, over-use of the full-stop (e.g. "....") can make a message
difficult to read.
Don't send irrelevant messages, especially to mailing lists or newsgroups. 
Don't send large attachments without checking with the recipient first. 
Don't send excessive multiple postings to people who have no interest.
This is known as "spamming" and is considered to be ignorant, and may
lead to serious trouble with your Internet Service Provider (ISP) or
IT department.
Don't conduct arguments in public, for example on a mailing list. 
Don't "flame" people by sending them abusive email messages. 
Don't make personal remarks about third parties. Email messages can
come back to haunt you.
Don't mark things as urgent if they aren't, because then when you
really do have an urgent message it may not be treated in the way it
deserves.
Don't post your email address on web sites and other public parts of
the Internet unless you want to be deluged with spam.

Also, you can find a list of 32 golden rules of email etiquette at
www.emailreplies.com, most of which speak to the very problems you are
dealing with.  You can print out copies, or just send the page as
"hint" (wink, wink).

Hope that helps.

Galactic Polyglot

alsinger

Just to add my two cents:

I think your core problem has nothing to do with e-mail etiquette.
Your objective should be to reduce the number of e-mails you are receiving.

As you are now already overloaded with e-mails , could I kindly suggest 
that if you are to try to do all the things the prior commentator has
suggested , then you will really drive yourself crazy.

So to really take the "Bull by the horns" here are some suggestions
- for now ignore any e-mails which  are cc to you. You are on the list 
  for information only.
- If the people in your section report to you , tell them that e-mails 
  addressed to you should not be cc to anyone outside of the group 
  (and especially not to your boss or high level management)
- Attempt to priortise all the e-mails addressed to you. Put those that do not 
  need addressing on the back burner.
- If there are still a lot of issues which still need to be addressed I would 
  suggest you might want to have a short daily meeting (15-30 mins) with your 
  group in order to resolve the issues. (again this assumes these people 
  report to you.)
- draw up an issues list from high to low priority and make sure someone is on 
  the hook for resolving them. (you may be responsible for some of the 
  issues)
- If the people in your section do not report to you, then you will need to 
  get the support of the section head to reduce the number of         
  requests/issues. Explain to him/her that you are overwhelmed. However use my 
  above suggestions as a possible solution.
- When things settle down then look at the e-mails still been sent to you .
  Ask that any subject which is important or sensitive is addressed to you  in 
  person.
- Again if the section reports to you be very firm on e-mails not been cc to 
  people outside the group or upper management. (too many people cc on e-mails 
  will cause all sorts of unneccessary noise) 
- In meetings with your group, enforce what is appropiate and what is not 
  appropiate to send by e-mail. Have clear guidlines as to when you believe an 
  e-mail is appropriate and when it is not. 
Mongolia

I propose setting up a web form and limiting the number of characters
accepted in a comment field. Then send yoursef a webmail based on the
data you collected from your employees in the forms.

Each employee could fill out a username and password to log in to the
web form and you could use that information to indentify them.

Good luck,
If you need a hand with webforms let me know.

Just set some guidelines on sending emails.  Ask people to summarize
requests and or comments in a systematic form at the bottom of their
terse emails.

Well E-mail Etiquette is similar to every application on the net...
the so called Netiquette....
But don't forget an E-mail was similar to a letter so if you want to
have an idea of a E-mail etiquette can be you can write down a letter
and that is what a correct E-mail must is...