A Guild is a lot like a pair of shoes, you really want the fight fit.
What world are you in?
Start with a self appraisal. What do yu plan to do with your city? What aspects of the game do you like and hate? Gow active a player are you? How much help do you need with understanding the game? How much help do you want to get from the Guild? How much do you want to help the Guild?
Once you figure out what it is you want out of the game, then it;s time to start looking.
Look at Guild Descroptions looking for Guilds that suit you. Check how they do in GE Championships, Guild Level, number of members. all fine measures of activity. Talk to members of prospective Guilds. Join prospective Guilds and immediately check their marketplace and their 'Guild Thread' in the message center, two more measures of activity.
Most Important (why did I list this last if it's important?) you are NEVER committed to a Guild Don;t hesitate to quit if you make a mistake in Guild Collection.
Like that pair of shoes, (Oh, that;s why, wanted to bring my metaphor full circle) if you and the Guild don't fit quite right, go get a something that does.
Any questions?
Good Luck!