For my two cents worth, I would have to say look professional and dress like one. If you dress like a bum(jeans and tee) then you give the impression that your work is less than professional. Whether it be chinos or dress pants and an oxford shirt(tie optional) and possibly a sport coat, gives an air of decencsy and respectability, and a show of pride in yourself that should portray a sense of pride in your product as well.