I just remembered how most people just seem to get along in their own groups and don't really do much talking to too many others. I've maybe chat with a few people here and there while standing in an autograph line nothing more. Now I will say that I'm not the best at conversation starting either but I can talk and talk and talk.
It can be tricky. I discovered ST fandom in early 1980. In Sydney, we had monthly marathons of TOS on the big screen (six, later five plus a TAS, or five plus an episode of "Zombies of the Stratosphere"), and everybody gathered in a large foyer for two intermissions. There were always loners and
chatterers, but mostly everybody could find someone to talk to.
At conventions and club meetings, I quickly realised that getting involved
- costuming, writing or editing fanzines, joining a newsletter collating party, volunteering to run or speak on a panel, MCing, etc - made me someone people wanted
to get to know. It makes it much easier to identify people with common interests, not just "Star Trek" in general, or you can find people with a similar sense of humour.
After a while though, you can
find yourself in a clique. You'll turn up at an event and choose to hang with a default group of friends, and not be as open to meeting new people. Certainly, it would be impossible for a shy person to break into a clique.
Wear an unusual shirt! Someone will come up to ask you about it!