JEE Main is one of the competitive exam there is lot of competition. You need to really work hard to get into top colleges. You should be determined and self motivated to achieve your goal.

If you have good hold on your basics you can easily crack your exam. If not you should start working on it take help of NCERT books for that. You can start with the topics which carries more weightage in the exam. You can make your proper time table.so, that you can easily complete your syllabus on time. Set your day to day and weekly targets and try to achieve them.
 
Below are the topics which carries more weightage in the exam

Physics

-Mechanics- You will find many questions on JEE which are directly from mechanics. You should also cover elasticity.

-Electricity and magnetism- A lot of questions are asked from the applications of Coulomb’s law and Capacitance. There are quite a large number of standard formula in electrostatics and magneto-statics.

-Thermal physics

-Fluids and waves and sound- There are lot of questions from this topic mainly from Doppler Effect.

-Potentiometer-related experiments
-Optics
-Modern physics

Chemistry

-Mole Concept
- Thermodynamics and Thermo-chemistry

Mathematics

Coordinate Geometry (3-D)
Application of Derivatives
Functions
Integral Calculus
Matrix & Determinants
Probability
Trigonometry

You can take help of previous year papers to know the exam pattern and level of questions.

Practice plays a very important role in scoring good marks and to increase your speed during exam. You should daily solve complete mock test series to analyze your preparation level at regular interval of time. It is very important to do complete analysis of your mock test series. So, that you can learn from your mistakes. Knowing your strength and weakness and regularly working on that is very important.

Give proper time to revision. Last 15 days you should only devote to revise your syllabus and don't pick any new topics on last days. 

All the Best for your Preparation!!