Optional Paper plays a very important role in the final merit list. If prepared well, it can enhance the final score of the candidate and be the difference between getting the top choice and missing the cutoff altogether. At the same time, an under-prepared optional paper may lead to a steep fall in the final marks and throw a candidate out of the selection list.

There are various factors that go into selecting an optional out of the given list:

1. Familiarity: If your graduation subject appears in the list and you have a fair command over your graduation subjects, then it is easier to choose an optional. Since, you would have already spent 3 or 4 years preparing the subjects during graduation, you can be expected to have a fair idea of the subject already. Apart from that, you would have access to the books, which you might have bought or would be available in your library. All these factors make your graduation subject an ideal choice for the mains exam.
2. Interest: Since an Optional subject would consume a high proportion of time, it is important to choose a subject of your liking. A subject in which a candidate has an interest is comparatively easier to prepare as reading books of the same subject do not feel like an additional burden. Apart from that, the Optional subject requires a greater depth of understanding as the question paper is of graduation level. In such a scenario, if the optional subject is of liking, then the study would seem like pursuing a hobby, which is the ideal situation. Here, one can try looking into the previous year papers to have a fair idea of the questions asked previously and determine the feasibility of preparing the optional subject accordingly.
3. Availability of Material: This can be considered as the single most important factor regarding a non-familiar optional subject. If enough material including notes, books, test series etc. is available, then there is no harm in going for a subject that is different from graduation subject. In fact, many technical graduates usually prefer humanities subjects like history or political science as their optional subject in the Mains Exam. The best approach would be to move around the market and try to look at the available notes. If the material seems adequate, then the subject can be chosen as the optional subject.
4. Good Coaching: It is a given that coaching is not essential for preparing for civil services. However, the benefit of coaching is that it simplifies the books and curates them according to the needs of the exam. Also, it might require a long time for a candidate to understand the requirements of an exam. Coaching makes it easier to understand the approach required to clear this exam. Therefore, if good coaching is available for an optional subject, then it will simplify the exam process for the candidate.
5. Performance of the optional: Another important factor which has become significant in choosing an optional is the proportion of selected candidates, out of the total candidates who wrote the mains exam with the same optional subject. In recent years, popularity of many optional subjects has decreased among the student community as such optional has fetched comparatively lesser marks for the candidates. For instance, public administration was the clear favorite of a large majority of students around a decade back. However, many students have discarded it in the favor of some other optional subject which has been related with the toppers in some recent years.