If you simply put in an application to a guild this thread won't apply to you so much.
I met my current GM on a Deadmines (VC) at level 18 back before there were summoning stones. We got together and had to wait for the others to show up. We did a few runs and eventually became friends. Off and on we would level together, and his wife would also be leveling with us. It was probably amazing for him, as he was leveling as a Prot pally and he had 2 priests following behind him. Eventually, over two years we split up and tried different guilds but eventually we ended up back together with a bunch of other close friends now that we met in WoW. Ended up being the top Alliance raiding guild in WotLK on our server. It's strange how a little dungeon run has really steered where my game was heading.
To this day there are still a few moments where one of us stops on mumble and says: "Holy crap, we met on a VC run in Vanilla?!?"
So what about you? Any odd/fun stories about how you met your guild?
A group of guildmates saved you from a ganking and you joined them?
Someone randomly gave you a mageweave bag and you decided to join them?