Understand the NTSE 2020 Syllabus. Check NTSE 2020 Exam Pattern. Understand your strengths and weaknesses. Take mock tests. Revise regularly. Get answers to your doubts.
You can join a coaching like Aakash or any other in your locality . They will provide you with appropriate study material. If you are doing self study ; then purchase NTSE book of Arihant. Solve it completely. Daily study for atleast 2 hours.
All the best friend!