Admissions take place at different dates for different universities and colleges. But, usually, the application form for admission is available from the months of March-May.
For merit-based admissions, first, the University releases the application form. After the date is over, the university releases cut-off lists. If your percentage falls under the range of cut-off list, then you are eligible to take the admission.
For entrance-based admission, the application stage remains the same. When the date gets over, university issues admit card. After the conduction of the entrance test, the university issues cut-off lists. If your rank falls under the list, you are eligible for admission.
Now, for example, the University of Delhi releases its application forms in the last week of May. After the application date is over, the university starts releasing its cut-off lists from the mid of June.
In Case of JMI and IP University, the application process begins in the last week of February and March respectively. After the last date of application forms, both universities release the admit cards and entrance exam dates for different courses.
For exact dates of application forms, entrance dates, etc., kindly refer to the website of the respective university under which you want to take admission.