For undergraduate courses, it's better to get your application form before your +2 results. Because by the time result is out, most of the seats in the aided section will be filled. So, as soon as your result is declared go to the respective department admission team and submit your application. If you are eligible, you will get admission. 

For postgraduation courses, admission starts around June. So, after your final semester, check the admission date in the respective departments.