I sold my WoW account and other MMO accounts on Ebay (they would get pulled sometimes other times I was able to sneak by). The way I did it was I listed everything I had for every character and such, made emphasis on very rare or not in the game anymore items. My WoW account for examply had 4 lvl 60's (This was a couple of months before BC came out) and I did have people want to buy just one of the characters but I didn't want to break it up. If you want to break it up, you can make a new WoW account under the name that your current WoW account is on then do a paid transfer from one account to the other of the character, but the accounts have to both be in your name that is the only way Blizz will transfer characters from one account to another.
You'll only make good money if you have a pretty nicely geared character and some fair amount of gold usually. Now, if someone buys your account you will give them the username/password but also the secret question and password cause that is how they can get help from Blizz is with that info, the secret question and answer can not be changed and the account will always be in the name of the person who originally made it, but they can change most all the other info.
For example, the WoW account I sold, I had 4 lvl 60 characters all in tier 2 epics except my main character (rogue) that had 5 peices of T3 and other goodies from Naxx and AQ40. I listed all my gear, skills, talents, how many times I had reset talents as that cost would go up each time (only to 50g, but I only ever respected 2 times), had all bank slots all with 18 slot bags, stacks abound stacks of rare herbs and all the alcehmly reciepes in the game, the original lvl 60 NE mount before they added the armor on it in the first patch, my account was a collector editions so it had the mini pet you could select and got with every character you made, how much gold I had, my rep with factions. You get the idea, I did this is great detail for my rogue as it was my main character and the highlight of the account (at the time T3 armor characters were not being sold as Naxx was only around for like 4-6 weeks so only higher end guilds even were getting far into it). My other lesser characters I detailed out equipment, skills, and all the other but didn't list all the other smaller stuff like rep unless requested.