Preparation is everything! If you feel prepared you are more likely to feel confident. Preparation may take many forms. If you have planned meticulously, researched thoroughly, this will make you feel very self assured. Perhaps you have practiced, had a dry run and worked through different eventualities. Your clothes can help you feel confident. You may feel comfortable in certain clothes or feel more confident when you have invested time and effort in the way you look. Looking good can also make you feel good and this can increase confidence. Whatever it takes to give you the edge and make you feel more confidence is worth doing.