how well is to prepare and write the NEET exam

Being one of the toughest exams, one needs a lot of hard work and determination to get good score in Neet.
First you should go through the entire syllabus. Then make a proper a programmatic study schedule.
Instead of choosing a random topic from the syllabus, you must break your preparation into sections. Sub-topics from each section should be selected and then strategy on clearing concepts must be made.
Whenever any doubt pops up in your mind, try to solve it by then.
Don't think NCERT books are less. According to toppers and experts, NCERTs are the best book to start your preparation with.
Don't forget about negative marking. Answer if and only if you are sure about that.
Revision is a must thing. At least 10 days before the examination you must start your revision along with short notes.
Give mock tests once you are done with your syllabus. Solve previous years' exam papers available on Internet. Then analyse it. Find out your weak areas and work on them.
Read all the chapters, ignoring low weightage chapters and studying only most important chapters can cost a lot. So study from first to last. During last few days of examination, you can focus more on the chapters with high weightage.

Some important books for Neet- For physics- HC Verma and DC Paney
For Chemistry- Physical Chemistry by OP Tandon, Inorganic Chemistry by JD Lee.
For Biology- Biology Vol 1 and 2 by Truman, Objective Biology by Dinesh, Pradeep guide on Biology.

Going by last few years' question analysis, we have the chapter wise weightage.

• Biology

Class XI-
Diversity of Living Organisms 14%
Structural Organisation in Plants & Animals 5%
Cell: Structure and Function 9%
Plant Physiology 6%
Human Physiology 20%

Class XII-
Reproduction 9%
Genetics and Evolution 18%
Biology and Human Welfare 9%
Biotechnology and its Applications 4%
Ecology and Environment 6%

• Physics

Physical-world and measurement 2%
kinematics 3%
Laws of Motion 3%
Work, Energy and Power 4%
Motion of System of Particles and Rigid Body 5%
Gravitation 2%
Properties of Bulk Matter 3%
Thermodynamics 9%
Behaviour of Perfect Gas and Kinetic Theory 3%
Oscillation & Waves 3%
Electrostatics 9%
Current Electricity 8%
Magnetic Effect of Current & Magnetism 5%
Electromagnetic Induction & Alternating Current 8%
Electromagnetic Waves 5%
Dual Nature of Matter and Radiation 6%
optics 10%
Atoms & Nuclei 3%
Electronic Devices 9%

• Chemistry

Basic Concepts of Chemistry 1%
Structure of Atom 2%
Classification of Elements & Periodicity in Properties 2%
Chemical Bonding and Molecular Structure 5%
States of Matter: Gases and Liquids 2%
Thermodynamics 8%
Equilibrium 6%
Redox Reactions 3%
s-Block Elements 2%
Some p-Block Elements 2%
Organic Chemistry: Basic Principles & Techniques 4%
Hydrocarbons 3%
Environmental Chemistry 2%
Solid State 2%
Solutions 5%
Electrochemistry 2%
Chemical Kinetics 3%
Surface Chemistry 2%
Isolation of Elements 2%
p-Block Elements 5%
d- and f-Block Elements 4%
Coordination Compounds 9%
Haloalkanes and Haloarenes 3%
Alcohols, Phenols and Ethers 4%
Aldehydes, Ketones and Carboxylic Acids 4%
Organic Compounds containing Nitrogen 2%
Biomolecules 3%
Polymers 3%
Chemistry in Everyday Life 2%

However, there are chances that Neet 2021 syllabus will be reduced as the academic year has been delayed and due to this pandemic all educational institutes are closed so it is difficult to complete the entire syllabus. To complement that, CBSE has reduced the syllabus 30%.
However, Careers360 has come up with Neet knock out package to help medical aspirants in their preparation. http://learn.careers360.com/knockout-neet-may/