Dear student, 

Hope you are doing well. 

Preparing any entrance has almost the same algorithm as other exams do have. 

So, the most important thing and the first thing you should is check the whole syllabus and read it thoroughly. 

Then you need to collect previous year paper's to have an idea of the pattern of the pattern. You should at least have a minimum of past three years question paper in hand with you from either some book stores or you can also get these online in their website. 

Then you need a book which mostly covers your syllabus. If not one you may have different books for different topics or chapters. 

Always start with the easiest topics first and be thorough enough that you can answer any question related to that likewise go towards the hard or hardest topics such as Marxism, liberalism  and many other easy topics which depends totally upon you. 

Spend more time in the topics which needs to get memorised such as the facts, acts, dates and lot more which have no logics and needs to get memorised. 

Lastly when you are done and confident,  just go through a bit of current affairs which is also important in the exams. That's all now are ready to appear in exams. 

Hope this helped. 

Good luck!