Before starting your preparation make sure you know about the complete syllabus.

Instead of reading too many books once for UPSC Exam preparation , read a few books many times. You should ideally be able to revise all topics thrice before the day of UPSC Exam . Focus on building the basics first by reading the NCERTs. Once you’ve gone through the NCERTs and made notes for ready revision, you can move on to the advance level books. It is not at all essential to read each book cover to cover. Spend some time analysing the UPSC exam question papers of previous years to understand questions from which topic feature regularly in the papers.

Work on your currrent affairs, you can read daily newspapers like The Hindu or The Indian Express.

Good Luck!!