Hi Aakash,

to prepare for JAM 2019 you first need to understand the syllabus of the subject of your choice. Preparing a time-table for study is another important stage. Prepare a timetable in such a way that you can incorporate time for preparation sample paper solving and attempting mock tests. in the initial few months, you could give more time for preparation and comparatively lesser time for solving sample papers. towards the last month, before the exam give more time for revision and solving sample papers and mock tests. this will help in understanding how much of preparation is needed before the examination. 

Refer to the below given article for more information: How to prepare for JAM 2019