I would only wear a tie if the rest of what you're wearing calls for it. Too many people throw on a tie just because they think it's professional, but the truth is, often times it can take away from what you're wearing. Personally I love nothing more than to wear a Ralph Lauren long sleeve button-up, slacks, dress shoes and a nice belt. Try to stay away from plain, easy-to-wear colors. If you want to impress them with what you are wearing, DON'T wear black slacks with a white button-up and a black tie. You might as well roll up on a bike with a Bible in your hand. If you're just trying not to look like a bum then it doesn't really matter. I really think wearing grey slacks (right style/color) instead of black will up your status big time. And quality products make a big difference.