Dear student,

Start your preparation with completing the ncert basics of 6 to 12.

Building the basics is the most important thing in upsc preparation.

After building the basics and making your own notes you can refer other books like spectrum for modern history, lakshmikanth for polity, etc

After completing 75% of the syllabus do previous year question papers which will help you to find your weak side and you can get an idea about the type of questions asked.

You should also be updated with the current affairs by using newspapers and monthly magazines.

Do revision and make your own notes and build a map in your mind about all the things you study.

Practice every question paper possible and gain a technique for calculated guessing.

All the best for your preparation

Hope it helped