chemistry is the second most important subject . Although it carries equal marks as in Physics but since it is comparatively easy ( your view might vary as personally I find Physics easier then chemistry). But since it takes less time it is definitely more important than physics.

(If you wanna crack an exam , forget about your interest and start studying according to what they want you to study)
Iam trying to divide the topics and giving approx question asked from each in past 10years
Physical Chemistry-

Everything is equally important here so can't say anything . Still Thermodynamics , electrochemistry and equilibrium have a slight edge over other chapters.

Inorganic chemistry-

This is going to be easy.

Chemical bonding- 68 questions.Periodic table - 24 questions.Coordination compounds- 24.

p block is important.
Organic Chemistry-

General Organic chemistryIsomerismReaction mechanism

Remember for organic and inorganic NCERT is the key.

First of all to get 120+ in chemistry you need to be good at organic chemistry in that also specially in aldehyde, ketone,  and nitrogen compounds like amine should be good.
In inorganic chemistry you need to be perfect in p block and d and f block. Also remember all the exceptions in all chapters.
In physical chemistry do chapters
Thermodynamics
Chemical equilibrium
Electro chemistry
Chemical kinetics

Hello, As per your query i would like to tell you, Most important for NEET/AIIMS is your NCERT books as these books include basic principles and concepts and provide accurate information
KEEP NCERT + ONE REFERNCE BOOK + MAXIMUM MCQS PRACTICE.
.First of all you should prefer NCERT for revisionFirst
take good command on organic chemistry.
I would like to mention some of the chapters:-
Class 11: Equilibrium,thermodynamics,p-block,s-block elements,general organic chemistry.
Class 12 : solutions, electrochemistry,surface chemistry,chemical kinetics,S and P block elements,polymer,biomolecules,alcohol,phenols and ether,amines and haloalkane and haloarenes.
These chapters must be prepared to ensure 120+ in chemistry and for sure!
Hope it helps
Regards
Dr Parmanand Agarwal
MBBS MD
Career counsellor.

Hello Sushant.

Hope you are doing well. Chemistry along with physics and biology hold good weightage in medical examination and thus having good conceptual knowledge in chemistry too is necessary. 

I would suggest you to firstly go through oragnic chemistry and have good command over it as it's really important. Especially the chapters such as aldehyde and ketones, and amino groups. Further in inorganic you should have the elements of pblock, d-block and d-block on your tips i.e. their trends, their reactivity etc. In physical chemistry you should focus on thermodynamics, kinematics and chemical equilibrium.

Moreover be thorough with all the exceptions and formulas. You can go for Pradeep's for physical chemistry preparation . Read inbetween lines from NCERT itself rather than wondering for different books. 

All the best.