One of the most important parts of landing a job is largely based on how well you do during the interview process.
From the moment you walk through the door, whether or not you know it or want to admit to it, you are being judged by the very people you may one day end up working for and with. Unless you are told otherwise, you should never show up to an interview in jeans and t-shirt. You would be surprised at how many people do this! Rather, when you are schedule to have an interview, make sure that you are dressed in business or business-casual attire. Business attire would be considered a suit and tie with a jacket and dress shoes for a male while for females, business attire could be either a pant suit or a tasteful dress/skirt combination with closed toe shoes and stockings.
If you have multiple piercings as a female, make sure that the only ones that are visible are two earrings per ear on the ear lobe (one per ear lobe is probably preferable). This means that any nose, eyebrow , cartilage or other facial piercings should be removed. If you are a male, there should be no piercings visible whatsoever. It is not acceptable for males to have pierced ears in a professional business atmosphere. Similarly, any and all visible tattoos should be covered up, as they do not give off a professional appearance.
When dressing for your interview, whether you are a male or female, avoid putting on any colognes or perfumes as doing so may irritate other co-workers, employers or people who work in the office area. For some reason, this continues to be a problem with employees who are interviewing for a job or who work in a professional setting. If you insist on putting on cologne or perfume, make sure that you only put on a minute amount so that it is barely noticeable. Instead of worrying yourself over smelling good with perfumes and colognes, try making sure that you take a thorough shower prior to your interview. Sometimes, all it takes is using a little soap and water to make you smell acceptable. Eat something small before you go to your interview so that your stomach won't be growling while you are speaking with your interviewers. Give yourself plenty of time to eat before your interview so that you have time to brush your teeth and floss. The last thing an interviewer wants to see is what you just ate for breakfast or lunch. Make sure that you keep your food choices simple as you also don't want to go into an interview smelling like fried food, etc.
Be comfortable during your interview but maintain a professional appearance. This means that you should speak audibly and clearly, give a firm handshake at the outset as well as the conclusion of the interview and always make sure that you are sitting up straight and never slouching. It helps to do a little research about the company beforehand, so that you can engage in some Q&A towards the end of the interview. Also, this shows that you are someone who takes initiative and is actively interested in what the company has to offer.