Hello Monika,

The CBSE has released the sample papers of all the subjects of all both class 10th and 12th.

You can get it downloaded from the official site of the CBSE.

Further I would suggest you to solve the sample questions of Oswal book and Arihant publication.

Analyse the answer sheet of toppers and try to solve the previous year question papers as it will help you to fetch more and more marks.

Good luck,

Hope it helps :)