The procedure for selecting optional subjects in the UPSC Main Examination involves a few crucial steps. Candidates must review the detailed syllabi and understand the subject matter well. It's advisable to choose a subject that aligns with their interests and previous academic background, as this familiarity can aid in better preparation. Furthermore, considering the scoring potential and overlap with General Studies subjects can be beneficial. Candidates often consult previous years' question papers and current trends to make an informed decision. Ultimately, a strategic selection increases the chances of securing a good score in the examination.