To assess their writing style for essays in UPSC, candidates should frequently review their written work, focusing on clarity, coherence, and structure. This self-analysis could involve comparing their essays against model answers to identify strengths and weaknesses. It is also beneficial to seek feedback from peers or mentors, as external perspectives can reveal aspects that candidates might overlook. Regularly engaging in practice essays on various topics can aid in honing one's style to address diverse prompts effectively.