Wear a dark suit of two components that were bought together as a suit, preferably a suit coat and pants for men and a suit coat and knee-length skirt for women.

Wear the suit with a white or light-colored, tailored shirt.

Recruiters suggest no visible body piercings. This includes pierced tongues. A single pair of small earrings for women is the exception.  Men are advised against wearing earrings.

Minimize jewelry in general. A wedding ring or class ring for men is acceptable, similar rings are acceptable for women.

No visible tattoos.

Hair should be well cut, freshly brushed, and not flamboyant.

While expressions of personality (touches of color, for example) may be acceptable, flamboyance, often perceived as an expression of self-centeredness, is typically not a valued attribute during the interview.

Backpacks and other casual carrying cases should not be combined with the suit.  A leather portfolio for note taking is acceptable.

Any overcoat should be business professional not Saturday casual. Hang it up in an appropriate storage area.  Do not carry it into the interview.

It does not matter if the interviewer is in business casual. You should be in business professional for your interview.

Sometimes companies invite candidates for a second interview or a mixer and specify business casual. It is extremely important in that situation that you use contacts within the company to determine just what business casual means to a specific company. Standards vary a great deal from company to company.

Men should wear a tie. Choose a conservative tie.

Sock color should match suit color.

Socks should be long enough to cover your leg under your pants.

Clean, polished dress shoes that completely cover the foot are the appropriate foot gear.

While pant suits are becoming more common, some recruiters view them as too casual.

For women, the safest suit choice for a positive professional impression is a suit with a knee length skirt, plain stockings, and shoes that are conservative pumps or low heels and completely cover the foot.

Recruiters have particularly identified whole shoes as the appropriate foot gear. 

Recruiters offer negative reactions to peep toes, sling backs, slides, sandals and other foot gear that leaves portions of the foot exposed.

Pair your suit with a crew neck or buttoned- up blouse.

Avoid shirts with low necklines.

The hem of the shirt should not show below the jacket hem.