Hey!

First of all, you don't need to get worried about your previous class scores as you will find many such students who have made a drastic change in their scores as compared to their previous year scores.

• Since you have taken commerce, make sure you solve and practice questions daily, as in revise whatever is taught in all subjects especially solving subjects like accountancy. You must make it in your schedule to study and revise the topics of accountancy on a daily basis or else you will face trouble in the subject.
• Solve each and every question of the books in each subject. You will get similar questions in your board exams as well.
• From the beginning, make proper notes so that it will assist you in revising the concepts.
• Whichever doubt you face, make sure to ask your concerned teachers regarding the query.
• Make it a habit to study topics of each chapter on a regular basis because if you start preparing before the exams, it would be too burdensome and it is most likely you won't be able to cover each topic.
• After completing of a chapter of each subject, you can solve the questions of that particular chapter from previous year board question papers.

All the best!