Welcome to my guide! First, I do not condone ANY of these practices (Buying & selling game items or accounts on E-Bay), this is because many people get scammed daily, and you may want to think before you buy. Before you even think about buying/selling items or accounts on E-Bay, first check the games rules, and make sure what you do does not go against them.

For safety, and copyright reasons, no game names, or game items will be mentioned in this guide.

Sections for quick research:
Chapter 1 Section 1: Accounts & Buying
Chapter 1 Section 2: Keeping it after you buy it.
Chapter 1 Section 3: A successful transaction.

Chapter 2 Section 1: E-Items, why bother!?
Chapter 2 Section 2: E-Items, what to look out for.
Chapter 2 Section 3: Sealing the transaction

Chapter 3 Section 1: E-Money, Game currency
Chapter 3 Section 2: Is this safe?

Well; here we go.

Have you ever seen a 'godly' account you wanted on E-Bay? Maybe you needed that great item, or some extra money on a certain game, so you buy it, but it doesn't come there as what you planned.

This guide is in 3 parts, Accounts, E-Items & E-Money. To search for a certain section, hold Ctrl + F on your keyboard to bring up the find/search menu.

Chapter 1 Section 1: Accounts & Buying

So you're searching around to buy an account for a game on E-Bay, could be for any reason, maybe you have money to blow, maybe you just need a spare account.
You find a seller, and you like the account, what is the FIRST thing you should do?
ASK QUESTIONS.
Many accounts on MMORPG's have people who will 'black out' stats when selling, most people want to know that these stats are, so that you will not be getting an account with a high stat in something, and very low stats in something else (Otherwise referred to as a 'pure'), if you don't care about those stats, then don't worry, but if you do, then you should ask, if the seller won't tell you, then figure the stats will be pretty low.
Other times people block out the second number in a stat, (For security, we'll say 9|=|), well what if the person just moved the 9 to the LEFT, put a black box in, and left it like that? It's not going against any policy, since it says the account is 9, it could have been considered an "accident".
If an account comes with items, that the person values at X amount of money, then think for a moment, some websites give different value prices then others, you should consider asking the seller where he/she gets their values from, unless it gives a list of the items included, then look and check for yourself to make sure that it equals out to that X amount of money.
An account is the biggest invest you will ever make to a game, you want to know that you will keep it for long periods of time, which leads us to section 2 in accounts:

Chapter 1 Section 2: Keeping it after you buy it.

Although it doesn't happen much, people sell accounts and then later change passwords back using secret questions/past buying records, or birth dates.
You want to make sure when you buy the account, it comes with everything that the game requires to change recovery questions, and if that means a reciept of payment, then so be it. NEVER buy an account without it's original E-Mail (And security questions to that, so you can change the password to it), the accounts security questions, and any other helpful information.
After you get the account, immediately change the password to it, if you really don't feel safe, change any information to make it 'yours' (Which may include security questions if possible). If you still don't feel safe, transfer anything of value to another account using a friend, or another method, and then later put it back when you feel the accounts safe.

Remember, its the biggest investment of the game, make sure its permanent.

Chapter 1 Section 3: A successful transaction.

It's all finished, and you bought your new account. Enjoy! But remember to play it safe, and before you buy accounts, make sure the game you play has no laws against it, or else you are running a risk of being banned after buying the account.

Chapter 2 Section 1: E-Items, why bother!?

Many people buy E-Items to invest in a game, years ago I bought a few items on E-Bay cheap ($10), waited a couple years, and now they are over $2,000. Great investment huh?
Investing can include buying discontinued items, promotional items, or just flat out items worth nothing now that may be discontinued someday.
You don't even have to be a gamer to make money on E-Items, you just have to know what to invest in, and when to do it.
Before you buy E-Items, look at your options, see how much other people sell for, and go with that before you sell YOUR E-Items. You want your items to be as competitive as possible in the E-Item E-Bay world.

Chapter 2 Section 2: E-Items, what to look out for.

Third party sites are the worst idea to look for when you are buying E-Items, and should be your last resort. E-Bay is by far the safest (And the cheapest) place to buy your E-Items. Third party sites can pull the take your money and run, and good luck paypal disputing an online sale with their (I have already delivered this item!), its your word against theirs, and unless this happens alot, their word wins.
Never cross-game trade (trading one games items for another games items), 8 times out of 10 its a scam, and one person is guaranteed to get ripped off (It is close to impossible to accept a 'trade' at the same time).

Chapter 2 Section 3: Sealing the transaction

Watch feedback when you buy on E-Bay, although a 0 feedback person may seem nice, sometimes you'll get a person who can be so much different after you buy, claim the price didn't get high enough, and take out features that you buy.
Again, paypal does not cover E-items with their protection, so good luck disputing something like this if it did happen. Does this mean all 0 feedback E-Sellers are bad? NO. I've had many successful transactions, watch what you buy, how you invest, and when you do it. Good luck! :)

Chapter 3 Section 1: E-Money, Game currency

Okay, so everyone loves having a little more money to spend on some cool stuff, but remember the 3 watching points of E-Money.

#1: Will this E-Money ever go down in price? Can I wait until it does so I can get 2x the money for the same price?

#2: Is this the CHEAPEST price on E-Bay? Will another seller give me it cheaper?

#3: Is their service credited to be the best by feedback or past-buys?

After you figure your right decision, then deal with the seller, most E-Money transactions are fast, and are done within 24 hours (If not, choose a seller who can do it in 24 hours).
Reccomendations for E-Money transactions is to have DSL, or something that does not hog up a phone line so the seller can call you to determine a time, although people on Dial-Up can get an E-Mail and set up a time in advance.

Chapter 3 Section 2: Is this safe?

First, think about the game your playing, some games have money-trackers, which track all trading, again, if it's illegal, EARN IT LEGALLY. Don't risk your account! 50% of all buyers of E-Money will get banned immediately, 25% will be banned in the future when proof comes up, and 5% might even be ratted out by E-Gold sellers who are being sued by the games company!
Then, make sure the seller is safe, is their gold prices too good to be true? Is their website in very poor english? You might be dealing with an overseas seller, which cause more problems then good (15% of overseas gold buyers claim that times for gold pickup would be 12 AM to 3 AM, too late for some, 5% report very poor english through the whole transaction, which lead to disputes with customer support, and 3% report not even getting the money at all).
In conclusion, watch who you deal with, make sure its safe, and make sure the seller can show creditation when you buy.

So, ending this guide, 3 do's and dont's.

3 Do's:

Invest.
Hold onto it.
Play it safe through the whole transaction.

3 Dont's:

Buy it illegally
Blow it on something thats going down in price.
Get scammed (Duh!)

Thank you for looking, and I hope this guide will change your mind about buying, or help you decide WHEN you buy.