In my humble opinion, one has to become a little 'wikipedia' for CSS. You must know at least the basic definition of everything that is happening. Realistically of course, that is not possible. But try to get to the nearest approximation.
In other words, for example if you are asked in exam about the Greek debt crisis in 2015, you must know at least the definition/core idea of the said topic. Similarly, you should know what tax-to-GDP ratio is even if you have never studied economy.
So, focus on the most important topics and prepare them theoughly. Topics such as Pakistan's economy, global terrorism, climate change etc are important. In the end, give some time to just quickly google all other terms and know about them.
This can help you tremendously in exam. That one definition or core idea can sometimes save your 20 marks question.
