The night before your interview ,try to have enough sleep,this way you get up with a fresh mind.The look is the first thing that draw attention to you,so make sure you shaved your face,dressed up elegantly .Drew a smile on your face,that is a remarkable sign that show your self confidence.
Once you get in to be interviewed,give a firm hand shake to the interviewer,and introduce yourself:Hi!I am so and so!the answer will be :Nice to meet you,I am so & so!how are you today?,and of course your answer will be :nice to meet you,how are ?
The way you start the conversation,will make you immediately feel confident .
Pay attention to your answers,they have to be correct,avoid street talk,slung words,that way,you give the interviewer an image about your education,and the way to handle further communications.
Having the qualifications to obtain the job is not always necessary,the interviewer may need just to know how much serious you are in your work,and if you are determined and having an eye for details.
Wish you best of luck.