Soy you have a head full of fandom knowledge: films, game statistics, movie notes, fanfic, etc. You're a great raconteur at a convention – so how are you going to use this on the job?
You're going to because your interests give you the ability to make small talk. You've got a valuable networking tool.
When you connect with people, you need to have something to talk about – despite what you may think, even business-oriented people like me don't talk careers all the time. Me, I want to have a chance to discuss Samurai 7, an awesome semi-steampunk expansion of the Seven Samurai (which, by the way, is real and is awesome).
All your fandom knowledge? That gives you smalltalk. That gives you something to talk to people about.
Now the image of the geek, fangirl, otaku who wants to only discuss their obsessions has been beaten into our heads by popular culture. That negative view probably keeps you from leveraging your fannish knowledge. However you have that knowledge, you can use it – and that stereotype about the annoying person who won't shut up can be true for anyone of any interest.
So first of all, appreciate the fact you have a lot of neat information in your head from your interests. You just have to know how to apply it when you want to connect with someone.
FIRST: Always take an interest in the other person's hobbies, fandoms, etc. first. People love to talk about themselves, and are often surprised when someone asks them about their interests. People are surprised and pleased to find someone take an interest in them. Besides, if you give them a chance, people are often fascinating.
SECOND: Figure out what you can share with that person, out of your interests, based on what you've learned from them. They may like historical train models and you may like cosplay, but you both have hands-on hobbies involving intense detail and odd materials – you can have a good laugh over shared stories of hunting up strange materials and pictures to build things just right.
THIRD: Don't be afraid to make or receive suggestions. Perhaps the above-mentioned train enthusiast may not want to go to an anime con, but might want to see a display of historical costumes you heard of. Perhaps you might hear of an interesting event to attend that you'd never thought of.
You're a geek. You've got Gundam episodes, fanfic ideas, video game unlockables, and Joss Whedon quotes in your head. Find a way to use them to sync up with people.
You'll meet some great folks – and you might expand someone's horizons, or your own.
– Steven Savage