Almost every industry demands a formal interview attire but it is also important to be know the norms of your own profession. In creative proffesion such as advertising a suit is always a safe but you may have more freedom in selecting a bright colored top. However, when in doubt, you should alway go in direction of formal and conservative. It is always better to be overdressed than underdressed.

To go a little more specific, here is a list of some things you should pay attention to when preparing your appearance for the interview. The only demand with your hair is that it should be clean and well groomed.
Women should wear natural looking makeup that will flatter and not overpower your outfit. Beards and other facial hair should be very neatly trimmed. Some industries may not like long hair or facial hair in general.

Nails should be always clean and well manicured. Perfume or cologne is not a good decision, as many people have adverse or even allergic reactions to it. Wear only a conservative amount of jewelry. Also, wear jewelry that flatters but doesn’t overpower. The thirteen rule is important here: no more than thirteen accessory pieces. If you have any type of tattoos or body piercing, consider how it will be seen during a first impression. Women should only bring in a purse or a briefcase, never both. Never bring a mobile phone into an interview.