Hello

To start your preparation, you should check the detailed syllabus and pattern of the exam. You should formulate a timetable and follow it religiously. You should devote time to each subject.

For physics, make sure to clear the basic concepts. Don't just mug up the topic, try to understand the concept completely.  
A good strategy and preparation material is essential to score well in the exam. Primarily, you should focus on the NCERT textbooks and should then refer other important books for in-depth knowledge. 
Make sure to learn all the concepts included in the syllabus ad solve all the numericals including those covered in the example section of the NCERT.
Important topics of Physics are-

Mechanics, Electrodynamics, Modern Physics, Heat and Thermodynamics, Optics, Simple Harmomic Motion, Waves.

Also, solve previous year question papers to have an idea about the types of questions asked in the exam and the difficulty level of the exam.

Good luck!