If you are capable to prepare yourself & your technical concepts are clear then take some good books of GATE,join some groups & forums.And you can clear GATE 2013 or join some GATE Coaching institute.
IUCAA (Inter-University Centre for Astronomy and Astrophysics) - NCRA (National Centre for Radio Astrophysics) Admission Test - INAT 2012
Last Date of Application-> Sep. 16, 2012
Exam Date-> Jan. 7, 2013 - Jan. 8, 2013