Job interviews are by definition moments of first impressions. Both men and women should make the most out of the opportunity by looking their absolute best.
Avoid Distracting Pieces

Loud ties or large jewelry items may distract potential employers from focusing on the content of your interview. Unless the job is in the fashion industry, one should dress to impress without distracting pieces such as large ear rings, gaudy necklace, loud ties or colored suits.
Know the Workplace Culture

A job at a bank or a law firm will have a different dress code than a tech company or a software company. Research the appropriate workplace attire and show up for the interview as if you are showing up for your first day at work.
Ask For Guidance

It's not like you have to go about picking your interview attire blindly. Ask the human resources manager about the company's dress code. It's his or her job to assist you in this process, so don't be shy if you have questions.
Groom To Be Neat

If you have a beard or long hair, regardless of your favorite hair style, groom all facial and head hair neatly. This means that if you have a beard, it should be trimmed. If in doubt about an acceptable hair style go for a conservative look and you can always grow your hair the way you desire after you get the job.
Choose Colors Wisely

The color of your suit or interview outfit should be a choice that meets the expectation of the job that you are interviewing for. When in doubt, blue or gray suits work as they match with more shirt, tie and scarf combinations.
Just One Spritz

Wear minimum perfume and cologne. How you smell should not be the lasting impression on your potential employer.
Leave The Watch Behind

Take your watch off when before you go into the interview. It will prevent you from looking down at it and communicating that you are bored or have someplace else to be.
Silence Your Phone

Similar to your watch, be sure to set your phone on silent before going into your interview. And yes, we mean silent, not vibrate. Feeling your phone go off while you're trying to sell yourself will undoubtedly make you lose your train of thought. Leaving it in your car or at home might be the best option for some people.
Be Comfortable

Whatever you wear, it should be comfortable so that you feel at ease during the interview. New shoes are hard to break in on the first wear and may cause you discomfort during the interview. Your outfit should fit and look good on you but it should also make you feel comfortable.
Polish Your Shoes

Wear sensible but polished and cleaned shoes. How some one takes care of their shoes is an indicator of how they see their self grooming. Your shoes do not need to be new but they should be polished and cleaned.
Default To White

If you're having a hard time deciding which colors to wear, just keep it simple. A clean white dress shirt or blouse can't possibly go wrong. Just be sure that you've ironed it.
Think Conservative

Pulling out all the stops is not as good of an idea as you think it might be. Interviewers just want to see that you care about how you present yourself, so a simple but clean look is the best way to go.
Double Check

Before the interview starts, make sure that all zippers are zipped up and all buttons are buttoned up. Nothing could be more embarrassing than realizing your fly is down in the middle of the interview.