People generally advise you to dress up at least two levels higher than the current job for which you are appearing. It will create a good first impression.
Never wear blue jeans while attending a job interview . Casual job interview attire is not advisable if you are serious in getting the job.
For clerical positions interviews, it is reasonable to wear long sleeved shirt with a collar, and nice pair of dress pants. Formal hard soled shoes will be fine. Women can wear casual pants with a sweater or blouse, with moderate heeled shoes.
The general rule is to opt for conservative shades and designs. Bright checked shirts, loud colored blouses, and odd designed dresses are not to be worn at all.
You have to ensure that the set of dress you have decided to wear for your interview is sparklingly fresh and without any crease marks whatsoever. Also ensure that the shirt is buttoned up fully when attending the interview.
