Google ICAO and its docs. Read them thoroughly. Also do a little research on human factors. Check out this website for the same.
pilot resources aviation resources aviation weather flight training for general aviation
Get yourself a question bank from one of the reputed tutors out there, it helps in revision. Don't forget tokyo convention, warsaw convention, freedom of air and the articles listed within.
Try the online question bank that cyril roy suggested in this thread as well.
In the end tally all that you know with the syllabus on the DGCA website.
Best of luck
