Answered by one of my successful student in IAS Exam-
You can clear IAS Prelims in one and half month if you put effort equal to 4–5 months preparation? Can you do ? If yes, then following is the strategy
- Read Lakshmi Kant for Polity
Here give more attention to few chapters like PREMBLE, FUNDAMENTAL RIGHTS, DPSP, FUNDAMENTAL DUTIES, UNION GOVERNMENT (Esp President and some portion of Parliament ), State government ( Esp Governor, Vidhan Parishad ), Constitutional Bodies like Election commission, UPSC, CAG .
Revise this and solve questions from Lakshmi Kant related with above mentioned topics - Spectrum for Modern Indian History
Focus more on different charter and council acts, 1857 revolt, Bengal split, Surat split (1907), Entry of Gandhi ji to 1947 in chronological orders. Try to tick on important INC session along with President name and outcome for eg- 1885, 1905, 1907, 1920, 1925, 1929, 1931, 1938, 1939, 1947 . - NCERT for geography
Read physical gepgraphy topics like Pressure belts, permanent & local winds, Ocean currents, salinity, temperature distribution, Fronts, cyclone, Rainfall, plate tectonics, volcanoes, types of rocks, atmosphere layers along with climatic region of the world from G C Leong.
For Indian geography, concentrate more on maps to locate, rivers, tributaries, mountain ranges (esp in southern India and north east) etc. - Environment from Shankar IAS book
Choose specific topics like International organisation related with Environment, Biodiversity, UNFCCC, Pollution, Endanger species along with location, National park with information like vegetation, climate type, endanger species . - For Indian Economy
Go through Mrunal’s videos and pdf - Current Affairs
Here you need to follow any good material like Vision IAS or Shiksha IAS Academy
Along with above you should solve one mock test daily without waiting to complete the syllabus, even though you do not know the answers of more than 30% questions. Practice is must!
I know its easier said than done but nothing is impossible. If you are not able to clear this time, at least it will help you in your next attempt.
Good luck!