If you are a student in 11 or 12, concentrate on your coaching classes to make strong base and concepts,and solve study material given by them,
If you are not going to any coaching classes or if you are a drop out,then you can buy HC vera book to build a strong base in physics. Read the book and solve problems.
Another book i always recommend is physics for medical aspirants by Dc pandey (arihant publications) very good book,conceptual ,a lo t of solved questions and previous year questions also there. I also recommend to buy a previous year physics question book by arihant publications where they give chapter wise questions of all medical exams. I also recommend to buy Aiims previous question papers book by MTG publications.
Never forget any equations at all,it must in in ur fingertips always,revise,do maximum questions repeat it again…u will succeed then..
In aiims,chemistry paper is of moderate level with concept based ,memory based and problem based.you should thoroughly clear your concept with ncert books.
Physical chemistry-study it thoroughly in ncert and memorise the formulas and practice as much as mcqs you can and graph based questions should be studied with formula should be in your mind.
Inorganic chemistry-it is basically memory based.you have to learn it thoroughly from ncert books and practice as much as mcqs you can.there is not such concept based questions.
Organic chemistry-it is very important portion of chemistry. Highest questions in chemistry are from organic.you first study thoroughly ncert books basically name reactions mechanism etc. After that practice mcqs related to these forms.
After studying ncert you may go through these books
Op tandon for organic
P bahadur for physical and in organic
Arihant objective chemistry by rk Gupta
After that do previous year papers.
For assertion and reasoning question you should study thoroughly ncert with clarity in understanding the topic will help you to tackle it.you may follow GRB or coaching modules for that
Don't skip ncert.make it your core book.