As far as I have seen, there is unfortunately only one way of accquiring extra Character Slots, that is through the ingame shop, which Anet has recently implemented. (you can find it in the upgrades section)
The downside to this shop is, that currently the only way to pay is through a Creditcard (Visa, Mastercard, etc). It is NOT possible to buy stuff in the shop by other means, like PayPal, acceptgiro, or any other way. Furthermore, the upgrades are not possible to be bought in normal retail shops, at least so far.
I think Anet made a misjudgement here, since Creditcards are only a popular method of payment in the US, and not as much in the civilized world. I wonder how many people are like me, want to buy character slots, but cant do so.
Guildmaster Cain
Desert Nomad
Guildmaster Aeron [Rt], Arthas Ironfist [W], Guild: The Tyrian Templars [TTT]
Joined May 2006

