What is your current guild, and why are you leaving?
Don't just say your reason for leaving the current guild is "to see more content." Presumably, everyone knows you're trying to see more content because you're raiding in the first place. Besides, what you're really saying with "see more content" is that "my current group sucks and will never progress further."
Instead, focus on the reasons you're applying to this particular guild. "I'd like to operate with a team that uses DKP," for example. "I'm interested in PvP," you might say, "and I see your guild does both raiding and battlegrounds together."
Of course, there might be raid leaders out there who're perfectly happy with "see more content." That answer's just a pet peeve of mine.
My answer: I'm looking to raid with a group whose priorities are similar to mine -- skill, hard work, focused effort. I don't have seven nights each week to play, so I make every second I do spend count.
Who are all of your your previous guilds?
This question has never made much sense to me; I think people are trying to keep an preventive eye out for drama hounds and guild hoppers. Maybe this is a roundabout way of asking for references. I've never used it on any kind of guild application because the answer rarely does me any actual good.
Of course, if someone like me is applying, my MMO guild history goes back roughly a decade. I guess I'd have to sort out if MUDs and MUSHes count to this guild. But if the guild you're applying to asks, you should provide a fairly accurate answer. It might be helpful to say why your relationship with each guild ended. And, by the way: this information is fairly public, anyway.
List your armory. Please log out in your raiding spec.
This is a no-brainer. The guild wants to check out your gear.
Are you willing to respec for the good of the raid?
Asking new applicants whether or not they're willing to respec is a heavy, heavy question. Many rogues, mages, hunters, and warlocks are relatively happy to switch specs if asked; they're just moving from one form of DPS to another form of DPS.
By comparison, however, hybrid classes are usually very nervous about answering this question. Some raid leaders aren't really asking you if you'll fine-tune your talent points or use a slightly different build; they're actually asking if a DPS hybrid "Will you heal?" or "Will you tank?"
You should be incredibly specific when you answer this question. If you simply say "yes, sure," then don't be surprised if your raid leader asks you to swap roles in a month, instead of simply altering your spec a bit. It's reasonable to ask someone to do what necessary in order to help the raid succeed, so if you don't want to fulfill a role, you should say so.
My answer: I'm happy to tank or DPS in about any configuration you want. I prefer to tank. While my class has a healing spec, I am about the worse healer to ever spam Flash of Light. I will do so in pinch, but I'm bad at it. It is not where my skills are located.
What do you, as a player, bring to our guild?
Many real-life interviews ask about the skills applicants bring to the table. This question is kind of the raiding version of that.
Don't try to cheese this question by saying something like, "I know every class in the game, and I have rocking DPS." That's not usually what a raid leader is looking for. What most raid leaders want to know are whether you're patient enough to wipe all night during progression. Do you regularly use free time look up current techniques? Do you communicate well in private environments? Try and illuminate the positive features that a raid leader would truly appreciate about you.
My answer: I have a fairly broad knowledgebase about the game, and am therefore able to adapt pretty quickly to whatever a raid needs. I'm well versed in all the fights, and know my two roles in those fights. I'm happy to be a team player, but also happy to help out wherever necessary.
How long have you been playing WoW? List your previous raiding experience. Which raids did you perform while the content was relevant?
These questions are natural and pertinent, although I think they're also the questions that Ghostcrawler's accessibility doctrine are slow diminishing. Raiding used to be a "hardcore" game; if you didn't have leagues of time and effort to pour into raiding, you didn't have much place in a raiding guild.
Nowadays, though, the access to quality gear through relatively comfortable playstyles means that anyone can raid. Still, if a "srs bznz" guild is looking to recruit "srs bznz" raiders, then they'll want someone with some miles under their tires.
My answer: Since beta, and all of it (with various degrees of involvement).
How do you handle criticism toward your performance?
This is the question I dread the most because criticism is such a subjective word. For example, I don't think there's anyone out there who would take offense if a raid leader said; "Wow, Bob! You do amazing DPS. Our tanks need a second or two headstart to be able to keep up with that; could you wait a few seconds before you unload?"
On the other hand, even I would get ruffled if someone told me "Hey, poopface, you're the worst ret paladin to ever faceroll!" (Okay, I'd actually laugh, but you get my point.)
Criticism and its delivery can be so bloody subjective that it's impossible simply answer the question. Heck, for every raid member that needs to learn to take criticism, there's probably one that need to learn how to coach.
In order to navigate this murky question smoothly, I answer with specific examples of how I've embraced coaching from raid leaders. This tends to demonstrate your willingness to work as a team, without making you come off as a complete newb.
Do you have a reliable PC? A reliable internet connection? Which Addons do you use?
These are obviously not questions most guilds could easily verify; you could claim to have a reliable computer and internet connection, even if you were using an aircard deep in the Sahara. But the point in the question is not getting details; it tends to be making you say so.
If someone swears their internet is reliable, and they start dropping their connection left and right, raid leaders feel better about having firing the raider if the question has already been asked.