Those candidate have completed 12th standard are eligible for AIIMS exam but your 12th standard subject must be Physics , Chemistry , Bio logy and English.
Also you must score 50% in all above mention subjects.For SC/ST candidate this percentage is reduced to 40%.
Your minimum age should be 17 years.
For AIIMS 2012 notification , You can apply for
I have attached the Question Paper of AIIMS entrance exam .So Please check it out.
For more details you can visit to http://www.aiims.edu