1. Understand the Basics:
Before attempting questions related to solid-state chemistry in the UPSC Chemistry optional, it is crucial to have a strong understanding of the fundamental concepts. This includes topics such as crystal structures, Bragg's law, lattice energy, defects in solids, solid-state reactions, etc.

2. Review Important Formulas:
Solid-state chemistry often involves the application of various formulas and equations. Make sure to revise and remember key formulas related to topics like unit cell parameters, coordination number, packing efficiency, ionic radii, Madelung constant, etc. Having a good grasp of these formulas will help in solving numerical problems accurately.

3. Analyze the Question:
Carefully read and analyze the question to understand what is being asked. Identify the key information provided in the question and determine the correct approach to solve it. Pay attention to specific terms and keywords that can guide you in the right direction.

4. Use Diagrams and Illustrations:
Solid-state chemistry often involves complex structures and arrangements. Utilize diagrams, illustrations, and figures to visualize the given information. Drawing crystal structures, unit cells, and defect configurations can help in better understanding and answering the question accurately.

5. Apply Concepts:
Apply the relevant concepts and principles to solve the question. Solid-state chemistry questions may require the application of theories like Bragg's law, Born-Haber cycle, Fajan's rule, etc. Use these concepts to analyze and solve the problem step by step.

6. Practice Numerical Problems:
Solid-state chemistry questions in UPSC Chemistry optional can often involve numerical problems. Practice solving a variety of numerical problems to enhance your problem-solving skills. This will help in improving speed and accuracy while answering such questions during the examination.

7. Refer to Standard Textbooks:
Consulting standard textbooks recommended for the UPSC Chemistry optional can provide in-depth knowledge and understanding of solid-state chemistry. Books like "Solid State Chemistry" by Puri, Sharma, and Kalia can be referred to for comprehensive coverage of the subject.

Remember to allocate sufficient time for revision and practice. Solving previous years' question papers and mock tests will familiarize you with the question pattern and boost your confidence. Stay focused, manage time effectively, and attempt questions with a calm and composed mindset.