The final interview is a formal interview and as such you should prepare as you did for your selection interview (i'm assuming you are going P3 - airman entry). You will know your provisional date for entry but please remember it is PROVISIONAL and need to convince the OC of the AFCO that you are committed, motivated and that your circumstances have not changed significantly to adversely effect your application. Commitment will be demonstrated by your knowledge of the trade you are applying, RTS and terms of service. Motivation will be demonstrated by what you are doing to succeed such as fitness, etc. The AFCO will compare your weight to what it was during your medical. If you have researched you will be confident and are likely to do well during interview. Remember what was asked at selection interview regarding NATO, Trade training and RTS and do much of the same but ensure that your fitness regime stands up to scrutiny. As Tony said, never lie and be yourself. Good luck and relax....remember I'm 'Here to help'