Start with reading NCERTS (class 6th to 12th)
Many of the aspects will seem unfamiliar or you will find it difficult to imagine and visualise few things. To make it easier have a look at some ANIMATED VIDEOS over internet ( animated videos and not some lecture).
Go through the BOOK LIST.
You don't need to go through all the chapters of all the books. But you need books as sometimes elaborate readings are required. Non of the notes available in the market can replace the standard textbooks. (Anyone claiming his notes is sufficient is not true - else nobody would be buying these books Non of the notes are sufficient to handle questions. For complex concepts you need to refer different sources. Having said that I will also want you to know that most notes will give coverage of around 75%-85%..but rest 15% is also important. Notes can be handy to zero down in the subject matter)
After reading the chapters and understanding the concepts you can start writing some of the answers. Start with direct questions and then you can then you can move to some complex questions which require interlinkages of the subject matter. This stage will require a lot of focus, practice and some guidance as well.
Geography is a subject matter which requires focus on flow diagrams ,maps, flow charts, pie charts etcetra. Try to incorporate these things in your answers.
Keep looking at Previous years questions. You will zero down on the areas which are more important. Read 100% syllabus but focus on these areas more.
Geomorphology by Savinder singh sir.
Climatology by D. S. Lal sir or By Savinder singh sir.
Oceanography, environmentalogy, Biogeography can be covered from Physical geography by Savinder singh sir. You will need help of current affairs to deal with these chapters.
Rupa publication -2 books -physical geography and human geography.
Evolution of geographical thought by MAZID Husain sir.
Geographical thoughts by Sudipto Adhikari sir.
Evolution of geographical thought by Dixit sir.
Models and Theories by MAZID Husain sir.
Reading NCERT class 11th and 12th is must for new comers and getting a feel for how to approach GS answers. GS and Optional answers should never look same.
Indian Geography by D. R. Khullar sir. (The knowledge of first paper and current affairs is sufficient to tackle the second paper. The answers in second paper must reflect your understanding of theories, models and other concepts from paper 1).
You don't need to read all books. Take help of these books in topics that you find difficult to understand.
You must collect case studies from news papers, Kurukshetra, Yojna, Geography and you magazine and down to earth website.
GEOMORPHOLOGY BY SAVINDER SINGH
Chapter-5: “Constitution of earth interior”
Chapter-6: “Continents and oceans”
Chapter-7: “Theory of Isostasy”
Chapter-11: “Plate tectonics”
Chapter-12: “Vulcanicity and Landforms”
Chapter-13: “Mountain Building”
Chapter-14: “Weathering and Massmovement”
Chapter-15: “Hillslope”
Chapter-16: “Cycle of Erosion, Rejuvenation, and Polycyclic Reliefs”
Chapter-17: “Denudation Chronology, Erosion surfaces and Peneplains”
Chapter-21: “Channel Morphology”
Chapter-27: “Periglacial Geomorphology”
Chapter-29: “Applied Geomorphology"
PHYSICAL GEOGRAPHY BY SAVINDER SINGH
Chapter-2 :“Origin of Earth”
Chapter-7: “Earth’s Movement”
Chapter-8: “Rocks”
Chapter-10, Chapter-12: “Earthquakes”
Chapter-12: “Plateau”
Chapter-13 :“Plains”
Chapter-14: “Lakes”
Chapter-18: “Running water(River) and Fluvial Landforms”
Chapter-19: “Groundwater and Karst Topography"
Chapter-20: “Sea waves and coastal Landforms”
Chapter-21: “Wind and Aeolian Landforms”
Chapter-22 :“Glaciers and Glaciated Topography”
The concepts can be easily grabbed if you focus on individual topics in isolation. It's more about memorization along with understanding.
Focus on following things :
1.Evolution of geographical thought by Mazid Husain : Focus on chronology.
2. Geographical Thought by R D Dixit :Chapter 1 to 8 and Chapter 11.
3. Fundamentals of Geographical Thought by Sudeepta Adhikari Chapter 11 and Chapter 13-16.
Keep looking at the previous year questions while reading these books. If you find it difficult to comprehend something then search over google and try to understand the concept.
The use of these perspectives and models will take some efforts and hardwork to apply in dynamic topics like environmental geography, population, settlement, resources, political geography or any other contemporary topics.
Perspectives in itself is easy. Memorise, revise, practice PYQs and you can deal with it.
Stay positive and work hard.