What to wear? The question you ask before a night out, which is also relevant to job interviews. And the right clothes for one are rarely right for the other.
As a general rule, err on the conservative side. The impression you want to make is one of competence, responsibility and being businesslike. Yet a navy 3 piece suit for a man is not always right, for example for a job in the media. For women, there is more variety in dress, but to work as a lawyer, a business suit makes sense. If you know the dress code for an industry or firm, this makes life easier, but if not you could always call the receptionist to find out.
Whatever the mode of dress, polished shoes should be well polished, ties tied properly, jewelery limited (together with perfumes and aftershave), hair combed, and accessories limited. And only one bag, man or woman. That saves a pause to gather everything together, and keeps on hand free to shake.