You've got your tickets, your sidekick, and your camera charged. You're ready to document the sights, sounds, and occasional smells at your first comic convention. But what to wear? While it's far from mandatory to be in costume, it is a lot of fun. Whether you've dropped the cash for workinng Iron Man armor or you're just looking for an easy comic book cosplay, you've come to the right place. I've been cosplaying for over ten years, and the basics still apply.
Consider Your Skills. Every once in a blue moon I meet someone in a perfect, elaborate costume who says it's their first. Usually these people are engineers, seamstresses, or artists - some profession which lends itself to creative skill. Start basic! You can do a lot with found pieces, thrift stores and dance shops. Remember, you'll likely be getting your picture taken, so doing your hair and a little makeup can do a lot for the presentation of even a simple costume. Guys - you too.
Make Sure it's Comfortable. That means put it on at home, jump, stretch, and walk around. You would be amazed - I have worn costumes with heels, contact lenses, and armor, but had the pantyhose be the worst part. If what you're wearing is uncomfortable by nature - some costumes just are - make sure you bring a change of clothes. Nothing's worse than having your day cut short or missing something special at the con because your costume prevented you from being there.
Represent Something You Love. The people you meet at a comic convention are a friendly sort, and a costume is a great way to let your freak flag fly. Try to pick something you'll want to talk about if people approach you - even if it's the costume itself! It's okay to say "I don't read a lot of Batman, but I really wanted to wear a Catwoman costume." But as the day wears on, the goggles dig into your head, and you're not into the character, you'll start to regret your decision to cosplay. Even if it's an obscure or simple costume, or just a cool t-shirt, you'll be happiest representing something you'll want to talk about with strangers.
Don't Overcostume Your Day. At multi-day conventions, I tend to take a day for major costuming and photoshoots, and a day where I wear a more simple costume, if any at all. Too much cosplay can weigh you down and take away from the convention experience. If you'll be meeting someone special there - a pro or a friend - and you don't want to be in a costume when you meet them, consider that - though the pros I've met have always been very happy to see cosplayers.
Know The Rules That Matter (And the ones that don't!) If your plan is to be a really accurate Poison Ivy with green paint and strategically applied fake leaves, make sure that's allowed at your convention. Many conventions have rules about family-friendly cosplay, and they can and will ask you to change if your costume is too skimpy, vulgar, or otherwise against their wishes. Additionally, while there are a great many rules with regard to competing in a costume contest, most of the competition rules don't apply outside of the contest. If your desire is just to wander the halls and get pictures with friends in comic book cosplay, rules about making your costume and having reference material don't count.