Short, in your own words, and read again within a day. That's what makes notes work.
Don't copy the book. Write what it means. If you can't, you've found what to ask about.
A heading per topic, bullets under it, arrows for cause and effect, a box for the exam points.
Notes on the right, questions on the left, a two-line summary at the bottom. Then test yourself.
Ten minutes the next day: fill gaps, underline key points. It saves hours before the exam.
How to Take Notes, with a ready Cornell page to print. Free, in English and हिंदी.