dear student,

Here are some tips for AIIMS entrance exam, that will hopefully help you get through with flying colors.
1)Most of the questions asked in the AIIMS exam are from the NCERT 11th& 12thstandard Physics, Chemistry & Biology books. So, if your fundamentals from school are right, then half the battle is won.

Chemistry: In the past, most of the questions have been NCERT-based. Hence, refer to NCERT books for practice. 
Biology: Follow NCERT & the Truemans series of books.

hope it helps....