Tamil Nadu Public Service Commission is conducted by government of Tamil Nadu for the recruitment of state civil services.tnpsc.gov.in  is the official website. This website can be visited for latest updates and results. This examination is conducted in three phases - Preliminary exam with objective type questions followed by main exams and interview. Candidate who clears all these rounds are considered to be successful. 

The preliminary exam will include questions covering the following fields of knowledge:General Science, current events of national and international importance , history and culture of India, geography, Indian polity, Indian economy, Indian national movement and freedom struggle, mental ability tests and other related fields. About 20% of the questions shall be exclusively with reference to Tamil, Tamilnadu, language and literature, culture and heritage of its people.

Below are the previous year questions papers given in question answer format.
2015 TNPSC Group 1 Preliminary Exam
2014 TNPSC Group 1 Preliminary Exam
2013 TNPSC Group 1 Preliminary Exam

In the below link, you practice the previous year question papers as sample tests.
2015 TNPSC Group 1 Preliminary Exam
2014 TNPSC Group 1 Preliminary Exam
2013 TNPSC Group 1 Preliminary Exam

Below are some of the useful link which can be referred for preparation.

Number of candidates taking this exam is increasing continuously. As competition increases, constant preparation is required to successfully clear this exam. We recommend you to take as many sample tests as possible, this will boost your confidence and helps you in understanding your strength and weakness. We wish you all the best for upcoming exams.