I know the following facts either because of my experience or what my school teachers who went for Board checking told us-
- Tougher the exam (as compared to previous years), more lenient the marking and vice-versa. So, I scored more in the exam which I was thinking was screwed as compared to the one which went great.
- Marking scheme is designed according to a particular word which one has to mention. That word is always the word mentioned in NCERT Textbook. For example, in inorganic chemistry, if answer is d-d transition or shielding effect, you have to write this word. If you explain it without writing this word, you will lose marks. Similarly in maths, while proving by induction, writing for all n>=1 is a must. So, underline these words when you are reading NCERT.
- In papers like English, your handwriting, margin and neatness matter a lot. Make paragraphs and write notice or message in one single page only. Not like half on one page and half on other.