On the first thought of appearing in the Civil Services Examination (C.S.E.), the first issue is the selection of optional. In a way, selection of right optional is the most crucial step. Post-graduates in any discipline, generally prefer taking up their parent subject for Prelims. Though such selection is quite logical, aspirants with any science discipline as their base subject must ponder over the issue more seriously. Maths, Physics, Geology etc., optional for Prelims must be opted for, only if one is out and out thorough with the subject. As UPSC ensures that 'some' candidates from every discipline must qualify for the Mains, aspirants with a science subject must judge themselves correctly regarding their own capability to be included in these 'some'. Some of the social sciences (e.g. History, Sociology and Public Administration) opted by quite a significant majority can, however, be a much safer bet, particularly for those (ordinary science graduates) who do not have any specific parent subject or for those who are not able to develop confidence in their parental subject. In either case, the formal preparation must start from the basic fundamentals, even if a person is already a post-graduate in that subject.
General Studies (GS) has to be prepared on quite a different plane because the content of this paper is too spread out and because any issue, major or minor, can be asked objectively. Traditionally, 10 + 2 level books of NCERT or any state education board had been covering a major part of the content but, these days, the items in news during the last one year or so, are being asked quite frequently. Problems are generally faced in everyday science (by the candidates with social sciences background) or in mental ability or in the fundamentals of economics. The most important aspect for the preparation of GS Prelims, therefore, is to identify the loop-holes and plug them urgently.
Many of you prepare a subject in terms of "reading" (once, twice, thrice etc.) with or without underlining the important facts. It results not only in longer time of preparation, but also many important points may skip. Also, even if you underline the highlighting points, most of you have the tendency to read the text in full while going for the subsequent readings. It is, therefore, advisable that texts must be read once and all important points (likely to be forgotten) recorded separately so that you need not study voluminous texts again. This would save on your time and should result in greater efficiency. The Mains: For right approach, the preparation of Mains should start before or at least concurrent with Prelims. Just because you have to prepare for Essay, GS and the two optional (English and a regional language, the one/two other compulsory, do not require a separate preparation) you never get enough time (to prepare for all these) after the declaration of Prelims' results. Further, while Prelims is only a screening test, it is on the basis of your performance in Mains, on which mainly depends the final outcome of your efforts. Strategically, therefore, the preparation for the examination should start about one year in advance and you should think about appearing in the Prelims only when you have had a strong grip over the Mains' subject matter.