Dress smartly .
Arrive on time
Dont be overconfident .
Dont be underconfident - remember you have done the Avtech course so are already more qualified than a lot of applicants even though you lack experience.
Do your research on the company and think of a couple of questions you can ask at the end so they know you have showed an interest.
Dont ask about pay and conditions at interview - if they volunteer the information fine but otherwise there will be time enough when they offer you the job.
Dont rely on overtime to get a living wage - when the o/t stops you will suffer.
Dont be afraid to ask the interviewer what they are looking for - remember you are making a decision as to whether you want the job as well as the company deciding if they want you.
Look at the interviewer when you answer the question - dont look around the room or at the floor .Take time and consider the question dont just blurt out a response.
Easy to say but stay calm and remember you are as good as the next applicant.
At the end of the interview ask when you can expect to hear whether you have been successful otherwise you will spend every waking minute running to the door for the postman or checking your emails and getting depressed ...
Good luck - let us know how you do . Hope this helps