So someone is whining on the Internet about how they didn't get called on during a panel at Renovation, and that they felt disconnected because they stood in a corridor and nobody talked to them. Not to say that Worldcons are perfect, but there are things people can do to have a better experience:
* Bring a friend. Sharing the new experiences with someone you already share context with makes it a lot more enjoyable. Not just during the con, but you can talk about things afterwards when you get home. It is much easier to start a conversation with your friend and then include other people than it is to break into someone else's talk.
* Volunteer. This is a must for me. Knowing what's going on brings a pattern to the whole experience, making it easier to understand and appreciate everything. You are much closer to what's going on and you are in much closer contact with interesting people, authors and other convention organizers, if you are behind some of the scenes.
* Bring something to the table. Give people a reason to talk to you. Be a writer, a fan writer, a costumer, a blogger, a filker, a maker, a gamer, whatever. If you are a fan, be a fan of something, and do something about your fandom. Show off your fandom with a t-shirt, a button, a hat; give people a clue that you can talk about something they are interested in.
* If you want to do something social, go to social events. Parties are social. Book launches, con suite, "stroll with the stars", workshops, kaffeeklatsches, and so on. Note the difference between social events and things that are more informational and structured. A panel is usually about the speakers; levels of formality vary, but if there are a bunch of famous authors at the front of the room, that's who people in the room want to hear. Maybe you can ask a question, but you are not the point of the panel.
* If you are interested in something in particular, do a bit of research and preparation. If you want to see an author, find out when they are doing a kaffeeklatsch or reading. Many authors have gatherings of their fans, which you find out about not through the Worldcon but through that author's blog or Facebook page or mailing list. Be a recognizable name on that blog or mailing list, so that when you meet the author in person, they'll already have a reason to talk to you. Don't just focus on the biggest names; people who only have a couple of Hugo nominations can be fascinating people but will be more accessible and more appreciative of meeting a fan.
This may not be a complete list but it's a good start. If you are doing this stuff, you will have a good time and you will be talking to people. Find one person to talk to, and build from there. Heck, find me, and I'll give you something to do. Once you are making fandom more interesting for everyone else, everyone else will start paying that back to you.