Use big words and correct punctuation, and grammar, and avoid I's and You's, and try to talk in 3rd person.
If I were a GM, I would honestly only ask for an armory link, and do the interview through vent, and have the person chat it up with some of the raiders in the guild, to see if the person would be a good fit. A guild can have the best players in the world, but if there isn't chemistry, the guild is going to fall flat on its face.