Hello,
I will share my experience of appearing in Css exam.
I appeared in Css 2011,and passed written exam and interview but could not qualify in the merit list.
Well still it was a very good experience to appear in the exam.
i think ,Css exam is not always about how much you know, it is mostly about how you present your concepts.
for beginners i will suggest to focus on following points:
*Aptitude(dedicated)
*Communication Skills(spoken+writing skills)
*Subject Selection
*Confidence
*Reading Books instead of key books etc

Prepare for the worst and hope for the best.
All the best.