Writing good answers in UPSC Mains is a skill.
Like all skills this can be learned.
Here's what makes for a good Mains answer
= Thread =
Disclaimer
Before we start, these are borrowed ideas.
Borrowed from:
• Gaurav Agarwal @crazyphoton (Rank 1, CSE2013)
• Anudeep Durishetty @anudeepd7 (Rank 1, CSE2017)
• Pratyush Pandey (Rank 21, CSE2019)
Even Pratyush and Anudeep mention @crazyphoton as the OG.
Structure
Your answer needs to have structure.
This makes it easier to read, and ensures that you have covered all parts of the question asked.
Let's look at what makes for good structure.
Introduction
Keep it simple.
Choose one word from the question and define it.
Quote facts or relevant articles if possible.
This one line about the topic let's the examiner know you've understood the question.
Example:
Body
Break it into 3 parts:
• Context - what has happened so far
• Main argument
• Counter argument
Give counter arguments (one line works) even when not asked. This adds another angle to your answer.
UPSC is looking for breadth, not depth.