To increase your score you should be aware of your weak points try to cover those weak points you will be able to score good marks in your exam. To know your weak areas and to improve them you can solve chapter wise test series and complete mock test series.

You should focus on important topics which carries more weightage in the exam.

Below are the highest priority chapters for JEE-

PHYSICS-

Mechanics
Electricity and magnetism
Thermal physics
Fluids and waves and sound
Potentiometer-related experiments
Optics
Modern physics

CHEMISTRY

PHYSICAL CHEMISTRY

Mole Concept
Atomic Structure

ORGANIC CHEMISTRY

General organicchemistry
Named reactions

INORGANIC CHEMISTRY

MATHEMATICS

Calculus
Co-ordinate geometry
Vectors (and 3D Geometry)
Algebra
Trigonometry

All the best!!