Preparing for the IISER entrance exam requires a solid understanding of science fundamentals and strong problem-solving skills. Here's a breakdown of the key subjects and topics you should focus on:

Physics:

Mechanics: Kinematics, Laws of Motion, Work, Energy, and Power.

Thermodynamics: Laws of Thermodynamics, Heat Transfer, and Thermodynamic Processes.

Electromagnetism: Electrostatics, Current Electricity, Magnetism, Electromagnetic Induction, and Alternating Currents.

Optics: Ray Optics and Wave Optics.

Modern Physics: Dual Nature of Matter and Radiation, Atoms and Nuclei, and Semiconductor Electronics.

Chemistry:

Physical Chemistry: Basic Concepts of Chemistry, States of Matter, Thermodynamics, Chemical Equilibrium, Electrochemistry, and Chemical Kinetics.

Inorganic Chemistry: Periodic Table, Chemical Bonding, Coordination Compounds, and Metallurgy.

Organic Chemistry: Basic Principles, Reactions and Mechanisms, Stereochemistry, Alkanes, Alkenes, Alkynes, Aromatic Compounds, and Biomolecules.

Biology:

Diversity of Living Organisms: Classification, Structure, and Function of Microorganisms, Plants, and Animals.

Cell Biology: Structure and Function of Cell Organelles, Cell Division, and Cell Cycle.

Genetics and Evolution: Mendelian Genetics, Molecular Genetics, Evolution, and Speciation.

Ecology: Ecosystems, Biodiversity, Ecological Succession, and Environmental Issues.

Mathematics:

Algebra: Polynomials, Equations, Inequalities, Progressions, and Mathematical Induction.

Trigonometry: Trigonometric Functions, Identities, and Equations.

Geometry: Euclidean Geometry, Coordinate Geometry, and Mensuration.

Calculus: Functions, Limits, Continuity, Differentiation, and Integration.

In addition to subject-specific knowledge, practice solving previous years' question papers and sample papers to get familiar with the exam pattern and improve your time management skills. Also, focus on strengthening your conceptual understanding by solving numerical problems and participating in mock tests. Finally, stay updated with current affairs in science and technology to tackle any general knowledge questions that may be part of the exam. Good luck with your preparation!