In order to get admission for 3 years law programme there is no any common entrance exam, there are only university level exams, So it is not very tough to clear, you can manage your college study & 3 years law entrance preparation for the particular university with little hard work. The top universities you can prefer:

University of Delhi, DULLB entrance exam

BHU- BHU LLb entrance exam

Government law college Pune- MH CET law

ILS Pune- MH CET law

Here are the preparation tips you can follow:

Plan a strategy for law entrance: Law Aspirants must schedule a study-plan. An intensive preparation strategy is needed  you must study at least two subjects every day and you must practice at least one vocabulary / English and one reasoning exercise daily.

Practise with previous year papers: Go through with previous year papers for the particular university exam & do practise as much you can, it will also give an idea about the exam.

Make you time Schedule for preparation: Make your time schedule separately for college study & law entrance exam. Firstly focus more on your college study.

Make your own notes: Make your own notes as per your convenience.

Join Mock test: Join Mock test as it will help you to analyze your performance where you stand.

Good Luck!