@Parineeta,

The interview of CSS holds key, as mostly it is a decisve factor and one needs to prepare well in order to get a good score, infact the desired allocation.
To start with i would recommend:
firstly prioritize the current topics which are often in limelight in one way or other. First make a list and intensively work on that.
Secondly get the editiorials of the dawn of the last two months, you need to scroll down only those which are concerned to you.
Thirdly work on your introduction and prepare well, it could be arranged from the top to bottom or from bottom to top( as far as educational career is concerned). The first question you would be asked before the panel is to introduce yourself, this is done in order to make yu calm, easy and relax.
Fourthly read dawn, news, and The Economist. Also watch bbc news and dawn news.
Fifthly you must also be well versed about the favorite personalities, favorite books, Events ( 3 national and 3 international events you have to write while filling the forms). The optional subjects are to summarised and need to be gone through again, so you can equip yurself fully well while handling the questions from the optional subject.
Sixthly work also on psychological tests as it is also a very important task before interview.
Lastly the most important one:-Give mock interviews to different people or group of people, they can be csp's or your fellows, even you can join any academy if you think and also sit before the mirror for an hour and talk. Remember by giving mock interviews your flaws can be detected, the more you are grilled the more you will be nourished and groomed. you will get the art how to handle an odd question which is at times unanswerable that is by practice. Also it is neccassary to have a command on spoken english. Rest is pray and recite this after nimaz Du’aa of Prophet Musa (A.S.) and send darood pak to Holy Prophet(SAWW)

Du’aa of Prophet Musa (A.S.)

From Surah Taha

Rabbi Ishrah Li Sadry, Wayassir Li Amry, Wahlul ‘Uqdatan Min Lisany, yafqahu Qawly.

(My Lord, I ask you to expand my breast, make my task easy, undo the knot in my tongue so that my speech will become comprehensible)

Best of luck.

__________________
Sweat in peace will lessen the blood in war.