Continuing where the other left off, here is what NOT to do at an anime con! :D
Don't randomly run around in your underwear.
I've seen people do it. This is an anime con, not your house. Just because people dress up and some anime characters have skimpy outfits, it doesn't mean it's a free pass to do whatever you want.
Don't harass cosplayers.
Even if they're your favorite characters, don't run and glomp them. Don't force them to do things the characters would, or make them act out your odd yaoi fantasies. THAT MEANS YOU FUJOSHI!
Don't touch things that don't belong to you.
I have a couple possessions that I don't want people to touch, including myself. At one con, I was wearing a long, black wig, and this person I didn't know was all touchy-feely on it. Sure, I was talking to thembut I never said they could touch me.
Don't glomp without asking.
It hurts sometimes, and I once saw someone get glomped with they were trying to get their stuff together. Surprise glomps are a no-no.
Don't leave your belongings unattended.
People steal and the chances of getting it back are near zero, even with security involved.
Don't leave your trash for others to pick up.
Don't insult other cosplayers.
Even if you think your cosplay is better than theirs. There's no reason to say it unless you want to be a jerk.
Don't hate a person because you hate the character they're cosplaying.
Those aren't the characters. They're real people. Differentiate between fantasy and anime, pl0x.
Don't go places alone.
Anime cons aren't completely safe. It's equally likely you'll meet some creeper at a con, as it is when you're walking around outside. Just remember, some pervs like anime, too.
Don't block hallways.
Don't take photos of artwork in artist alley.
This rule might not be enforced, but it's ILLEGAL. If you want the picture, buy it.
Don't try buying Yaoi, Yuri, or Hentai if you're underage.
These are 18+ items. You shouldn't even be reading these if you're not 18. Do your parents know?
Don't be an idiot.
Use common sense.