Great post Who, a great summarization of the guilds.

One thing I'd like to add is that if you're looking for a guild, don't spam "can I hAz a gild invite plox?" (obviously exaggerated). If someone wants you in their guild, they will send you an invite, however be wary of their guild and then refer to this post for assistance.

Even the 'best' or most 'well known' guilds may not be the best guild for you, be careful of who you join.