There are too many conventions to list in this space, but here are a few of the biggest names you may have heard of:
- Comic-Con in San Diego - while this one has 'comic' in the name, it's huge and has a large science fiction aspect.
- Dragoncon in Atlanta, Georgia
- Star Trek Convention in different cities including San Francisco, Las Vegas and Chicago
- Worldcon held in different locations in the US
- Philcon in Philadelphia
- Milehicon in the Denver area
- Eastercon based in England
- Fan Expo Canada
- Gallifrey One - for fans of the British television show Dr. Who
Gamers may get a chance to compete in tournaments at some cons. This includes role-playing games (RPG), board and card games, live-action role playing (LARP) and video game contests.
Many fans are so inspired by their favorite films, TV shows and books that they create art work based on the genres. Art shows are held at some local and larger cons which are usually judged by a panel. Not only do you have the opportunity to win but you gain experience and recognition by fans. You might even become one of those artists who creates a business from your love of the genre.
At one Michigan convention I attended, a charity raffle was held to help a local family. This is a common theme you may see at cons near you. Sci-fi con goers are a creative bunch and you'll find themed parties and contests of all sorts such as trivia, filk (music specific to fandom), cosplay make-up contests, themes for kids and crafts.
The prizes may be small or large including recognition awards, art work, autographed materials to cash and a chance at fame on the con circuit. Some cosplayers are well known for their ingenuity with costumes. Be sure also to check out the social media sites for the cons you plan on attending. Some of them give away prizes including free passes to the events via Facebook, Twitter, Pinterest and Google+.
I've focused on science fiction cons, but fandom is far reaching, so there are also cons held specifically for fans of anime, comics, gaming, horror, and furries. However, there is a crossover of fandoms, so you're very likely to find a sci-fi con with some other elements featured. Upcomingcons.com, sfsite.com, worldcon.org and scificonventions.com have listings for upcoming events. Have fun and good luck!
For more info on costuming, visit my article about Cosplay Contests for ideas.