Well i was taught some basic skills for interviews before...
Firstly, always try to keep your calm, be confident, its the key to a good interview. Also, don't forget this, its important. Brush your teeth and rinse it well so it smells damnn good. This helps in your overall confidence (really really works, you won't feel as comfortable with bad breath right?)
Secondly, as mentioned, try to maintain eye contact, don't let your eyes wonder about, if u are really nervous, maybe try to look at the interviewers forehead instead? Don't look at the floor whatever your do, and try to keep your hands away from other body parts, like scratching your neck or whatever.
Thirdly, watch your speed of talk, don't go too fast! be conscious of this, but not too much, or u will be read off as very nervous. Alot of people tend to speed up as they talk and from what i know, interviewers hate this. Just try to pause once in awhile to remind yourself, but try not to go "errr... ahhh" too often.
Lastly, your personality counts alot! yours is a cooking competition, so you do not have to pretend to be someone else, be yourself, be honest and be determined.
Well thats what i can say for now, it all depends on yourself really, all the best for this competition man! hope i helped abit..