I'm trying to figure this out as well. I currently have ten "friends" on my facebook. Most are old friends I don't see or even communicate with very much at all (if ever) and a few others are some of their friends who I don't really know well and don't ever talk to. The reason I got a facebook account was to try to connect with people from my current school, however, I've felt too unsure to ever "add" anyone because I don't know anyone all that well. At most, there's a few kids who might say "hello" in the hall or maybe talk to me for a few minutes if class is slow, but I still don't know if it would be appropriate to "add" them.
Nice avatar, by the way. I'm a major "Pumpkin Head".
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"I've been really, really anti-social for the past few years, and I'm just starting to get over it, and come out of my shell, and be able to like people again" - D'Arcy Wretzky