Hi Dejvu,
I just had my interview last thursday, Nov 7 in Kuala Lumpur. I guess you will be having the same interviewer as me as they told me that their next destination is HK. They are pretty nice people so dont worry so much.
The best advise is be cooperative with everyone and smile a lot. Yes, it's very tiring.
I dont know much about this body language business, but like what stellar said, just be relax. Dont slouch and try to look interested in everything they said or being discuss. Remember to give some input and PLEASE dont talk too much. No joke here. Those girls who talked too much didnt make it thru the first stage. A lot of group discussion.
I read from previous candidates, they said they did some psychomatix test. I didnt do that but I had a very simple english test. Dont worry about the weight/height. I am not sure how much the guys' weight/height but you should do fine.
Forget about the gel... but keep it tidy. small amount of gel should be alright.
Let me know how the interv went. I got eliminated after 4th discussion. What a luck!
Good luck