I've recently taken to delineating people's social preferences with Facebook.
When invited to an event, I look at the invitation list and write down all of the people I know (luckily, Facebook puts these people at the top of all the lists). Then I view the mutual friends I share with the inviter and mark off everyone who was on the invitation list. From there you can see who wasn't invited to said event.
It sounds too obvious, that people wouldn't be careless enough to essentially make accessible whom they do and do not like, but sure enough, a recent event invite I received led me to a list of people someone clearly didn't want to invite somewhere. Sometimes it was informative, sometimes it was confirmative.
It's fun!! I even made a spreadsheet! ("X's Who's In and Who's Out List")
I've started making webs based on who invites whom to events when they're being discriminatory, who writes on whose walls and with what frequency, who appears in photos with whom, etc. Well, started. Then I realized it was a massive task and abandoned all efforts to demarcate clique boundaries (which are fluid, anyway, and whose connections are non-binary) w/o some studied method.