Hello Santosh

Start reading newspapers. Not newspapers like Times of India(I would suggest that the first thing you do is throw out that newspaper), but papers like The Hindu and The Indian Express. They are very good and I would suggest you read them religiously.

Start reading NCERTS. These are basic textbooks which will give you the gist of the subject and then you can go deeper and deeper into that subject. For example, for history, you should start reading India's Ancient Past by R.S. Sharma, then Medieval India by Satish Chandra and then India's Struggle for Independence by Bipan Chandra. Then you can read textbooks which go deeper in the subject.

As you read the newspapers, make notes of important events. I have made 8 divisions, namely, International Relations(Middle East and Asia), International Relations(Americas and remaining world), Government Policies and schemes, Personalities and Awards and Sports, International Organisations, Social Issues, Economic Policies, Defence. I classify all news in these categories. These will help as a ready reckoner while you are revising for the general studies syllabus.

Don't restrict your reading to only books. Read sites like Quora. They will provide you with knowledge which can't be gained by reading books.

Make use of the Internet. Watch documentaries like BBC's Days that shook the World which will increase your knowledge base. Keep in mind that they tend to be a bit biased though.

Visit the websites of government ministries whenever a new bill is introduced. It will help you see the government point of view on the bill.

Read at least 4 of the following magazines: Frontline, Civil Services Chronicle, Economic and Political Weekly, India Today, The Economist, Yojana, Kurukshetra.

Whenever any current issue comes up, look up all the details on the internet, including the history of the issue in question.

Decide your optional fast and then look online for the recommended reading list for that optional.