One thing I've noticed about the 3d, animation, gaming industries it that the attire that everyone has told you about in business class or from your friends working in other industries, doesn't always fit. Wearing a suit might make you stand out, but in a way where you might not fit the profile of what they are looking for. Some studios are laid back, some are more business centric. You really have to know your audience.
First and foremost, do your research! Look into the studios you are applying to. Everything is on the web these days. It shouldn't be too difficult to figure out the vibe of certain studios. I'm not exactly sure how to describe this, but looking up a company before you go to an interview is always a good thing. Trying to figure out their vibe through their website isn't so easy. There are a bunch of studios that are becoming more social. Reaching out through LinkedIn and Facebook. Its not just on their website these days. Some places have head shots of their employees. Are they wearing suits? Are they wearing t-shirts? Looking for simple hints like that can help you figure out their 'vibe'.
Let's say the studio you are applying to has a very casual vibe. T-shirts and jeans type folks. Should you wear that to an interview? Hell no. Should you wear a suit? Please don't. You don't want to look like you couldn't care less. But you also don't want to look to anxious for the job. No one actual likes the eager beaver. We tolerate them. Some more then others, but that all depends on how much they know and how well they do things. For this situation, you should dress clean and appropriate. Nicer than the regular t-shirt and jeans. Go for a nice shirt. Maybe something that buttons up. And nice pants. Now, you can still do jeans, but please make sure they look clean and there are no oddly places holes. I might avoid the ripped jeans look. Ladies, if you are gonna wear a skirt, please make sure its not too short. If your finger tips can go past your skirt when you stand straight, you are wearing something that is probably more suited for a night out on the town and not a job interview. Try again. Also, low cut shirts are just distracting. Remember, this is a job interview, not a date. You want them to hire you based of your talents (at least, this is what I'm hoping).
Let's say they are the opposite. Its a very business attire type place. Well, then you should be dressing that way. I have not gone into any studios that have had that type of vibe. Maybe it exists, but I'm just not aware of it (this is where I ask you all to inform me if I'm wrong and make me update this whole post later or address it in a new post).
A job interview is definitely an important way to show potential employers who you are and what you can bring to their company. But not everyone has just an interview. I've worked at a few places just on word of mouth. I've also been to a bunch of job fairs. Word of mouth is difficult to dress for. On your first day, you should put some effort towards your appearance. For job fairs, well, it really depends on the job fair.
I always find jobs fairs kinda weird. You show up, stand on a bunch of lines and hopefully the person you are talking to has the information you're looking for. You hope they are looking for an artist like you. That their upcoming projects might need a person with your talents. Job fairs are tricky. You just don't know who is going to be there and it might be an impossible task to research them all. I've been to a job fair where they did not list which studios were going to be their ahead of time (well, they did. It was just they didn't list what locations they would be in. Kinda important to figure out if they are gonna be in your city or not. And they know who they are). For job fairs, I say the same thing rings true here as it did for the interview section. This is going to be the first impression. You want them to remember you, but you also want to make sure its a good memory. You don't want to be the slob they saw walk in who looks like they might not have showered this week. Clean up and make sure your leaving the right impressions.