Scoring 90% in your class 12th board exam requires consistent effort and effective study strategies. Here are some tips to help you achieve your goal:

1. **Set Clear Goals:** Define your target score and create a study plan accordingly.

2. **Organize Your Study Schedule:** Create a timetable that covers all subjects and topics, allocating more time to subjects you find challenging.

3. **Quality Study Time:** Focus on productive study sessions rather than the number of hours. Avoid cramming and prioritize understanding concepts.

4. **Use Effective Study Materials:** Choose textbooks, notes, and online resources that align with your syllabus and are easy to comprehend.

5. **Practice Regularly:** Solve previous year's question papers and sample papers to become familiar with the exam pattern.

6. **Take Breaks:** Don't overstrain yourself. Take short breaks during study sessions to refresh your mind.

7. **Healthy Lifestyle:** Maintain a balanced diet, get enough sleep, and exercise regularly to stay physically and mentally fit.

8. **Seek Help When Needed:** If you're stuck on a topic, don't hesitate to ask your teachers, classmates, or even use online resources for clarification.

9. **Revise Thoroughly:** Allocate time for revision before the exams. Review important formulas, concepts, and key points.

10. **Practice Time Management:** During the exam, manage your time wisely. Don't spend too much time on a single question.

11. **Stay Positive:** Believe in yourself, stay calm during the exam, and stay positive. Confidence can go a long way in achieving your goals.

12. **Mock Tests:** Take mock tests to simulate exam conditions and improve your time management and test-taking strategies.

Remember, scoring 90% requires dedication and consistent effort over time. Don't be discouraged by setbacks; learn from them and keep moving forward. Good luck!