Goldmarble said
I have to agree with Magnum, you need to dress somewhat fittingly for the type of work you're being interviewed for.
Pretty much this. Wear the clothes you would wear if you were going to be your own boss at this job -- so like, if you're applying to McDonald's or Gamestop or retail, dress like a manager; if you're applying for construction, dress like a foreman (minus safety gear).
Generally you want to demonstrate just a couple of things at your interview:
1.
You have your shit together (you can dress the part, you're not on drugs, you show up on time and you're not a lunatic). Playing the 'I need this job' card hurts you here.
2.
You're serious about working *specifically* here. Nobody wants to spend three months training you up and then suddenly you're on to better things.
3.
You're not going to be a problem-employee. Problem-employees come in many shapes and sizes; they're seeking this potential in you, so they can weed you out. Don't let them.
4.
You'll give them more than you take away. Jobs are business, business is money, money has to make sense. Be a hard working contributor, know your role, etc. The resume can really help on this one -- highlight things you've done, teams you've been on, etc. that went far and accomplished a lot -- the more involved you were, the better.
In terms of 'how should I act in the interview itself,' don't be **too** worried. You might be nervous -- everyone is nervous, nervous isn't bad. The person interviewing you *probably* isn't your future boss -- it's someone who's seen a ton of interviews and can sort out the normal people from the assholes. That's their job. So.... don't be an asshole, pretty much, and you've done the best you can.