Whether it is a small value thing or a big value thing we all consider different factors like how will be the thing useful to us, what is the payment mode, how good is the item for the price to be paid etc., before buying it. Similarly there are many factors to be considered when you think to buy WoW accounts.
Besides the price of the WoW accounts there are many other things to be considered before buying them. Among all, security is the most important thing to be considered when you go to buy WoW accounts. The first step to ensure security is to make sure that the existing WoW account was bought from an original owner of the account by entering into legal contract.
After this look for the type of customer service offered by the company so that you are not put into a difficult situation in case there is some problem with the account. Most of the companies will offer live customer support through phone, chat and email. But do not rely on the words instead check for yourself if all the service options are working properly and available in reality by just making a mock call, chat or email.
Now you would like to see how good is the account you wish to buy. For this you can look for user feedback or customer reviews included on the websites. Generally sites will include at least one review from the customers. Go through few of the feedbacks. To be surer look for third party user feedbacks because feedbacks displayed on parent site are less likely to be authentic then those included on other websites. More positive feedbacks will of course mean that the account is good and the site offering you to buy WoW accounts is a genuine one.