Preparing for the numerical-based questions in the IIT JAM Chemistry exam requires a systematic approach and practice. Here are some key steps and strategies to help you excel in this section:

1. Understand the Syllabus:
- Familiarize yourself with the exam syllabus and the specific topics that are covered in the numerical-based questions. This will help you identify the areas where you need to focus your preparation.

2. Strengthen Basics:
- Develop a strong foundation in the fundamental concepts of chemistry, including topics such as stoichiometry, thermodynamics, chemical kinetics, atomic structure, and molecular spectroscopy.
- Revise the basic mathematical concepts and formulas required to solve numerical problems.

3. Refer to Standard Textbooks:
- Consult standard textbooks recommended by experts or your professors to study the concepts in depth.
- Understand the derivations, formulas, and equations thoroughly and practice their applications through numerical problems.

4. Practice Regularly:
- Solve a wide range of numerical problems from previous years' question papers, sample papers, and practice books.
- Focus on solving problems from each topic and subtopic to ensure comprehensive preparation.
- Gradually increase the difficulty level of the problems as you gain confidence.

5. Time Management:
- Develop time management skills by setting time limits for solving problems.
- Initially, focus on accuracy rather than speed. As you gain proficiency, gradually work on improving your speed without compromising accuracy.

6. Analyze Mistakes:
- Analyze your mistakes and weak areas while practicing. Identify the conceptual gaps or errors that led to incorrect answers.
- Revise and clarify these concepts thoroughly to avoid similar mistakes in the future.

7. Seek Clarification:
- If you encounter any doubts or difficulties while solving numerical problems, seek clarification from your professors, mentors, or subject experts.
- Participate in group study sessions or online forums to discuss and resolve doubts with fellow aspirants.

8. Mock Tests:
- Take regular mock tests to assess your progress and identify areas that need improvement.
- Analyze your performance in these tests to understand your strengths and weaknesses.
- Work on refining your problem-solving strategies based on the feedback received from mock tests.

9. Revise and Consolidate:
- Regularly revise the topics and concepts you have covered to reinforce your understanding.
- Make concise notes or flashcards to revise important formulas, equations, and concepts quickly.

Remember, consistent practice, thorough understanding of concepts, and effective time management are the key factors to excel in the numerical-based questions of the IIT JAM Chemistry exam.