What's the point of going to the interview and not dressing the part? Nothing! ALL interviews have an expectation of attire. So why not make the best possible impression by dressing the part.
Depending on the position you are going after:
MEN - a dark suit, white shirt, stain free tie and polished shoes are most appropriate.
WOMEN - a dark suit (pants or skirt), modest accessories and respectable shoes are most fitting. I be you are wondering about the respectable shoes... sandals and stilettos are never proper for a professional interview (so put them away)!
Office and Non-Professionals:
MEN - slacks or khakis, clean button down shirt, matching sports coat and tie preferred.
WOMEN - matching skirt or pants with blouse, modest accessories and respectable shoes are most fitting. See not above about respectable shoes :-)
Skilled, Semi-Skilled or Operative Positions:
MEN / WOMEN - khakis, polo shirt and clean shoes. Sometimes, jeans and work boots are more appropriate for tradesman, especially in construction related fields. You may be hired on the spot and expected to start work immediately.
If you have a question about attire, you should ask.