What you wear defines who you are. Professional dress is different for every interview you are going to go into. You should never under dress or overdress, find out the dress code ahead of time. Different jobs under one company require different dress. A radio emcee will most likely not dress the same as the manager of the station. It is always safer to dress up more rather than less to show that you are serious about the interview. Appearance is the first thing an interviewer sees, so make it memorable and appropriate.
In the world of advertising there seems to be more leeway in which one can dress. It depends on the job title and the size of the company, if it is a small company, large company, old company and/or new company.
There are many ways to find out what is proper dress for an interview. You can check the company’s website, visit the company before the interview or ask other people in the field for their opinion. Many times information can be found online. You want to make sure you dress the part but not to overdress the future boss.
Business dress for men:
Ø Suit (solid or very subtle weave pattern or plaid)
Ø Long sleeve shirt (white or light blue)
Ø Belt (matches shoes)
Ø Tie
Ø Dark socks, conservative leather shoes
Ø Jewelry (conservative watch)
Ø Neat, professional haircut
Ø Portfolio or briefcase
Business dress for women: 
Ø Suit (navy, black or dark grey)
Ø Skirt (appropriate length is long enough to cover thighs when sitting)
Ø Coordinated blouse
Ø Conservative shoes (closed toe and no high or chunky heels)
Ø Professional hairstyle
Ø Light perfume and makeup
Ø Portfolio or briefcase (some believe to use a portfolio or briefcase instead of a purse)
If your job calls for a suit for work in the advertising business you should probably consider the size of the business. If it is a smaller business a suit is not always required, unless it is for a big meeting. You can usually get away with wearing jeans. Bigger and newer companies that call for suits usually mean you should dress as if you work for a bank.
Proper dress includes business, business casual and casual. Dress ranges anywhere from business suits to casual jeans. For a big company as well as a small, creative dress does not change. As a creative you can wear jeans everyday, even with sneakers and nice shirts. You still have to look nice because you want to build credit for yourself as to have good reputation.
*Photos: Creative Commons http://search.creativecommons.org/