We often tend to get nervous during interviews and end up saying what we should not. The best way perhaps is to be precise about what you are saying, answer in brief but to the point, keep a cool head by giving a neutral thoughts to the questions that are being asked to you. Don't try to expose your knowledge all at a time rather wait till the time you have been asked to speak about it. Stay cool and composed throughout the interview!!!
If you going for interview means that you have somewhat knowledge. First you must know where you are for interview.Knowing that company you decide your position. So dont afraid do what you want with confidence.Don't take any kind of pressure.