I know a method like this has already been posted, but this is just a different variation. So far, I've had a 75% work rate.
So, with the "scourge invasion" recent event, and all the hype over Naxxramas, I thought this little scam up. YES, this can get you banned, but often they don't even realise they didn't get the promised 'rep'.
So, make a level one alt. Name him something believable. Don't name it something rediculous like "Supagnome".
Send mail FROM your alt to your main. You HAVE to actually make the letter believable, as it is used in the later part of the scam. I used this as the content of the letter:
"Thank you for aiding us in our fight against the Legion of Kel'Thuzad. Recently, as you've already been informed, a large group of the Kel'Thuzads minions invaded our outposts accross Western Plaguelands. Many of our men died, and many buildings were destroyed.
We thank you for your kindness. Your efforts will not go forgotten, Champion."
Anyway. This has to be from your ALT to your MAIN or another alt, so that when you send the letter to your victim, it doesnt say "Plain letter, Written by <Name other then your alt>.
Confusing, I know... but it does work very good.
So, once you've sent the letters from your alt to your main, you must send them back to your alt.
Put them in a CoD message to your victum. I usually ask for 10g -- something very reasonable. You must also make a body for this letter, as well.
I used:
"Greetings and salutations, <Name>. I am writting this letter on behalf of the Argent Dawn. Recently, our outposts were invaded by minions of Kel'Thuzad. If you wish to aid us furthar, more details can be found in the attached document. Your donations will not be forgotten, <Class>."
Yes, I know both of my letters were lame, but they work.
Anyway, so now you have a letter on your alt, written by that char.
Go to a mailbox, put the letter in the item slot, and CoD for 10g. Then, you must type the second letter, seen above, in the normal letter part of the mail.
Send, and check back later! =)
Enjoy. As I said, it does work. Sorry for the vague instructions and any typos there may be. I'm incredibly tired.