Make sure your hair is clean, neat and styled. Nails need clean and groomed as well. Limit jewelry and accessories, remember to wear a watch. Perfume or cologne should be light fragrances and never strong. Avoid chewing gum during an interview or smoking before an interview.
Professional dress can vary from field to field.
It may be helpful to talk with people employed in that field and ask their advice. When in doubt, choose a tailored, conservative, simple and neat look. Always check your appearance before meeting an interviewer. Greet the interviewer in a friendly, business-like manner, using their last name. Introduce yourself in a confident manner.