Welcome to this prestigious forum. You will really find this forum helpful for your preparation of CSS.
6 months time is enough if you work hard and follow guidelines of senior members of this forum. Next year exams are expected to be held around March 2010, so it's almost a year left.
To start with, I quote my earlier suggestion to an aspirant:
I suggest you should start reading DAWN newspaper regularly, esp. the Front page, back page, international, World in focus, Friday Feature and editorials etc. This would help you in compulsory subjects like Current Affairs, Essay & English, Islamiat, and some optionals e.g. I.R.
Wish you all the best.