The concepts
Like any other language, Sanskrit to have definite concepts and grammar which you have to learn. The basic rule here is learning and memorizing everything possible.
The essay questions
In the Sanskrit exam paper you will find a number of questions which require essay type answers. They are the highest scoring questions and you can simply memorize all of them. Most of the questions often get repeated for years and by keeping a hold on the older exam papers and practicing them, you can easily understand the pattern.
The NCERT books
These books are your holy books for the exams. You literally do not have to check with one single book in the market other than your NCERT books for Sanskrit. Nothing goes around these books and they have all the material you need to score 100 percent marks.
The key is grammar
The Sanskrit Grammar is quite easy and simple. You do not have to do a lot of work on it. Once you are familiar with the concepts in it, practice the question papers you have along with some mock tests.
Listen to your teacher
The Sanskrit teacher of your class knows the best way to score marks. She can tell you every single bit of information that you need. Do not skip any class and make sure to make all the notes required.
Write everything
Sanskrit is all about practice and you can memorize everything required by writing them repeatedly. In Sanskrit, the more you write, the more you will remember.