Hi,
For your class 12th preparation I will suggest you to do thorough study of ncert books and practice previous year questions so that you understand the pattern of questions asked in exams.
If you are a commerce student then there are some subjects or topics which are common in both CPT and class 12,study them thoroughly as it will help you in both exams.Maintain proper balance while preparing for both exams as gap between both exams is very limited.