A clean, neat, tidy and well-groomed presentation will go a long way to securing the job. Also being slightly overdressed is much better than being underdressed. Once dressed have a good critical look at yourself in the mirror, once satisfied you can proceed with confidence. A good idea is to photocopy and bind all documentation which will enable the copy to be left behind for further perusal - a nice touch. Prepare the folder with the executive summary at the front with supporting detail at the back if needed, do not include irrelevant detail.
Nerves are a common occurrence but can be overcome.
Often nerves feed on themselves and will definitely degrade your performance at the upcoming interview. Knowing why they occur will help in overcoming the fear factor. The other plus is that your lungs are filling deeply which assists in modulation and continuity in speech during the interview. At the interview On meeting the interviewer shake hands firmly, take a deep breath and introduce yourself calmly and clearly. Maintain eye contact, try to relax and be genial, a trick some find that works is to imagine that the role is reversed and that the interviewer is coming to you for the job and you are wanting to make him feel at ease.