Whenever you begin preparation firstly go through the syllabus (Prelims and Mains)and go through past year papers of UPSC so that you will get an idea of what actually UPSC expects from you and could get a trend of the exams
Next thing you need to do studies NCERTs and do writing practice.
Preference should given to buy OLD NCERTS which are according to old syllabus as they are more relevant to UPSC studies. Here is the list of must do NCERTs.
History – for history you can do Modern Spectrum RAJIV AHIR for prelims …apart from that one can also prefer GROVER for MAINS …u need extensive reading …sky is the limit …still you can go for BIPAN CHANDRA Part 1 and Part 2 ….India before Gandhi and India After Gandhi by Ramchandra Guha could be done. World history can be done through Un-academy videos and Vision handouts.
Geography for prelims Geography …one can do GC Leong ISC certified Physical geography …and a good ATLAS of Penguin publications should be referred ….for Mains NCERT will be suffice.
Economics: for Economics prelims i recommend SRIRAM IAS notes along with Ramesh Singh of Tata McGraw Hill publications. for Eco Mains ..having hold on newspaper is very important. I would recommending following Economic Times or Business Standard or Mint (selective reading)
Political Science: for Polity Laxmi Kant is the Bible need to done byheart 20 readings minimum for Prelims for Mains i would recommend visiting prsindia.org for continuous tracking of all kinds of legislation proposed, drafted and passed in Parliament along with reports of various Committee reports along with this reading newspaper editorials relating to Constitution, Judicial court judgements, etc need to be studied
Sociology for GS MAINS following books are recommended
Indian Society – Ram Ahuja
Social Problems in India – Ram Ahuja
Fine Arts for culture i would recommend referring to CCRT website, NIOS culture notes are good and current culture events should also tracked selectively. Also NITIN SINGHANIA notes on culture are handy.
Science for Mains , emphasis must be given on current science events like achievements of ISRO , inventions by BARC, DRDO and various Indian institutes…apart from this ‘major’ international inventions and discoveries must also be tracked
ETHICS: for ethics one may begin with LEXICON , emphasis has to be given on thinkers foreign and Indian thinkers …..their teachings must be reflected in the answers and case studies to earn more marks
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Apart from all this u’ll must surf a lot on Internet … go for editorials of multiple newspaper.. should follow magazines like
Yojana
Kurukshetra
Down-to-earth
Science Reporter
Swarajya Magazine
Wizard magazine for PIB stuff etc.
…..should also follow VISION notes , insightsonindia , mrunal.org, gktoday , etc. and off course my blog ?