Choosing a legit website should be the primary thing.
Some players will only pay attention to the price and delivery speed, but what about the gold collected in illegal way? Many players make mistake here, when they choose a website, the first thing they do is comparing the price, the cheapest wow gold suppliers often take advantages there. But if the price lower the market too much even lower the cost, customers should do more consideration now, because the gold offered by this supplier will be risky, in most case, this kind of gold is collected in illegal ways, which will lead their customers' accounts in troubles.
Make sure the order information is right
As there are many servers in Wow, please fill in server, faction and character name carefully. For if players fill in the wrong information, and it's happened someone just share the same information on that wrong server, the gold will be sent to the wrong guys. But in most case, a legit company will confirm their customers order information before make deliveries.
---What about if a buyer fill in the wrong information after payment?
If a buyer make this mistake, don't worry, just contact the site's online support or msn or some other effective contact method at first time, as long as the website the player choose is legit, this problem will get corrected very soon
Don't place large orders with a company that you have only done business for one or two times.
Players may have a pleasant business with a website for one or two times, but it doesn't mean this will be the never-changing rule there. Because the appearing of gold sellers are like mushrooms, but most of them are just flash in a pan.
What's more, for players' account aspects, it's also not smart to place large order with the site that they have done few business. Because Blizzard will not suspend players' accounts easily only for one or two times gold trading records, if this website don't know the rule of large gold trade it will lead the players account in troubles. While as far as most wow players recommended, Mmocarts.com is the few one that knowing this rule and no players meet problems when buying from them.