Candidates applying for the Civil Services must be Indian nationals (between 21 and 28 years old) as on August 1, and for the Forest Service, as on July 1 of the year of the examination.
In order to appear for the combined services examination, the candidate must have at least a Bachelor's degree in any discipline from a recognised university. In order to apply for the Forest Service, a candidate must have a Bachelor's degree in any of the science subjects.
Selection for the combined civil services takes place in three stages : A preliminary examination, a main examination, and a personality test.
The preliminary examination is a written test comprising of two papers. It is conducted every year in the month of June. The first paper (general studies) carries a maximum score of 150 points on 150 questions, with a time limit of two hours. It covers six topics - Indian History, Constitution of India , Geography , Economics, Science, and Current Affairs. The second paper is an 'optional' that is on a subject of the candidate's choice. This paper carries 300 points on 120 questions and is two hours long. Both papers are set in the objective type format.
Around 10,000 candidates are selected after the preliminary exams, which are taken by approximately 1,50,000 students every year.
The main examination is also a written test, which is held around November / December every year. It comprises two language papers (one in English and the other in an optional Indian language). Marks gained in these papers are not computed in the total score, but passing in both is compulsory for qualification. There are also two general studies papers (300 marks each), and four papers on two optional subjects (300 marks each).
Approximately 2,000 candidates are selected at the end of this stage, for the final personality test.
The personality test / interview, conducted in April / May every year, forms the final eliminatory stage. Conducted in the form of an oral interview, it enables an expert panel to judge first hand, the candidate's personality, ability and aptitude for the work. The personality test carries 250 points in a total of 2,050 points.
There is also a medical test, which is conducted before the allotment of services. It is an especially rigid test for those aspiring to join the IPS.
Roughly 800-900 candidates make it through the final selection each year, out of which the top ranking 100 candidates (approximately) are appointed to the IAS.
Selection to the Indian Forest Service , on the other hand, is on the basis of a written test held in the month of August every year. The test comprises: two compulsory papers (General English and General Knowledge) ; and additional papers in any two subjects chosen from the following options: agriculture / botany / chemistry / physics / geology / zoology / mathematics / agricultural engineering / chemical engineering / civil engineering / mechanical engineering , excepting combinations of agriculture and agricultural engineering , chemistry and chemical engineering.