Starting preparation during graduation is best decision because of so many reasons like career, job, age and other factors. Candidate's mind is uncluttered unlike people who have done their graduation and are undergoing some coaching. It’s a fresh canvas and flaws in the students can be easily identified and plugged. Lets discuss a strategy stepwise, which a cadidate can use :-

Firstly A strong foundation

• Understanding of Syllabus
• Read all basic NCERTs before reading reference books
• Start Reading Newspapers.

If you are Totally devoted to preparation and studying for 8-10 hours initially, this step should be covered in less than 2 months.

Secondly develop content base.

• Reading of basic study material/reference books
• Mastery of World Geography, Science and Technology, Geography, Indian and International Economy, International Relations, Indian Polity, Governance, History, Heritage, Culture and Society throuh coaching or seolf study
• Background of events and World problems

This stage should take 8-10 months of time

Thirdly Relate Things and be exam ready

• Having gone through the two stages, all the students will be prepared to take to study certain degree of correlation ship between the topics. Elevate the level by adding extra information and analysis. Develop an analytical ability as well and keep expressing it.
• In this stage, the candidate must go deep into prelims preparation that should comprise of practice and practice and practice
• In this stage, go for preparation of Mains and focus has to be on appearing in tests and developing analytical abilities. It has to be Revision, analysis and Tests. This is what should become the norm till the mains Examination.

During this process, you have build a strong foundation and give performace. Becuase at the end, result matters. So few important things: