Read the forums and see how the different guilds interact with other people. See if it appears to be a close knit guild or not. Is it an active guild or pretty quiet?
Decide if you want to e in an already established guild, which has it's ammenities already for you, or a newer one that is just now building ground up. Both have their advantages and disadvantages.
Let people get to know you though, and don't be afraid to turn down guild offers that don't suit your needs.
