The way you wear..........  

For me,I will wear smart,say long sleeve and a formal tie,which I believe will give my targeted job a plus.The men interview me would first know me by the out looking then my other abilities.Thus,I think it's very important!LOL

Most interviews I have ever been to I have always worn something smart,its not done really to turn up for any kind of interview dressed very casually,unless they state it in the letter beforehand,I will wear a suit of some sort,trouser suits are fine ,if its warmer weather then a skirt suit is better with a cotton blouse underneath,and some smart shoes.

I think it all depends on what kind of job you are interview for. I would recommend no matter what job you are going for you dress well. You should always wear a suit and tie. It just shows the person you are meeting with that you are serious. I have never went on an interview in a tee shirt and sneakers to a interiew. even if that job was in McDonalds

That really depends on what kind of job you are applying for. If you are applying for a white collar job (executive to management), it's better to dress formal. If you are applying for operational jobs, I guess there's no need to wear a tie and be too formal.
If you are applying for a job in the creative line, perhaps t-shirts and jeans may be perceived as acceptable.