Hello Fellow aspirant

Class 12 is a good time to start preparing for NEET also.

The topics you have to study for NEET, about 50% of those topics are for NEET, JIPMER and AIIMS too.

I will advise you to study for boards first. Go though each and every topic and ask if you do not understand something.

After studying you can take out one hour and solve past year questions.

Boards score is important too so I would suggest you to focus on your Boards first as they will be coming first. 

Prepare a timetable in such a way that equal importance is given to every subject. Revise every chapter. Set targets for example :- Target for Monday is to complete 3 chapters from each subject. Now revising 3 chapters won't take much time. After Boards you can solve multiple choice questions of each subject everyday . If you have already prepared notes well and good, if not then you can make notes of formulas which are helpful for revising before exams. 

Solve previous year questions . Also refer previous year questions of Boards. 

If you still have any queries feel free to ask in the comment section down below.