Dear Saona, one of the basic criteria to be eligible to attempt NEETA is that you should have scired a minimum of 50% in your 12th with Physics, Chemistry, Biology/Biotechnology and English as your core subjects. Its 50% for General Category, 45% for PWD and 40% for SC/ST candidates. If you dont meet this criteria, then you aren't eligible to write NEET. 

Hey Sapna 

in order to appear for NEET the criteria is that you should have passed 12th standard from a known board with minimum 50% in physics, Chemistry & Biology 

category wise the percentage is different so if you mention your category that might be helpful.