This really depends on what kind of player you are. When I started out, I was interested in getting into a guild so I could train better and not be just playing ps by myself. Later on, those members moved to the hack and slash server. I joined another, for no good reason and stayed there for a while even though i wasn't crazy about it. Finally, I wanted to learn about role play, so I did some research on the forums and narrowed my choices down to either the dark empire or the outlaws, and tried to contact a member about joining.
I think in summary, you want a guild that matches your goals.. look at it as a vehicle or a means to get there.