Hi,

The syllabus of examination of each posts are available in the official website of TNPSC

http://www.tnpsc.gov.in/syllabus.html

The syllabus may vary every year so please check the syllabus published in the official website for preparation. You haven't specified the post of the exam you are giving so an accurate answering is not possible. However once you get the syllabus you can start collecting previous year question papers and state preparing for it. You can also check study materials available for particular exam and prepare with the help of it. All the best.