here I am listing down few points please keep it in mind

1. The most common misconception among NID aspirants is that if you draw well, then you can crack NID, which is totally false. Though good sketching is essential, the questions are framed to judge a candidates creativity, imagination & visualization skills/ observation / general awareness etc. So, developing these skills are equally important.

2. Be Creative - Creativity is a mysterious trait. Many people have tried to define creativity in their own ways but there is no single universally accepted definition. It is difficult to summarise in a few lines but we can say that creativity is the ability to come up with new, original ideas which are not conventional. It is the breaking away from the stereotype, routine, accepted set of thoughts and possessing a deeper insight to problem solving. In short, a creative person experiences rebirth everyday with his or her ideas.

3. Understand that your drawing & creative skills are useless if you are not able to present your thoughts in the exam in the limited amount of time. You stand to lose marks for the questions you fail to answer or which are left incomplete, it doesn't matter how good you are at your work. So speed is equally important.

5. Don't practice in A3 size sketch books. Work in A4 size as that is normally the standard size of answer sheets in the examinations.

6. Don't mug up G.K. books but be more aware about what is happening around - Read the newspapers regularly. Increase your observation power. Try to find out about people who have genuinely contributed to the field of design, their innovative works etc. Read books / magazines & develop a genuine passion for your field.

7. Find your own deep and compelling reason to successfully clear NID. Motivate yourself. Work with enthusiasm & you will be amazed at your ideas & creations.

8. In questions requiring drawing, always draw with a light hand first, doing mainly the outlining without the details. When you are satisfied with the proportions & the rough outline, you may finalize. You will save a lot of time that students normally waste in erasing & re-drawing.

9. Practice more with dry mediums ( colours ), as they are convenient to use and take less time in exams.

10. Plan your time for school/college study & NID entrance preparation. Use your time effectively with a time table.

Hope you find it helpful

let me know in the comment box if you are having any further doubts

thanks

Good Luck!