Pre-boards give the environment of a real exam, so here's a two months preparation strategy for pre-board exams.
Most board exams, be it CBSE or ICSE or State Board are held in February/March. Class 12 students will be appearing not just for board exams but also for JEE Main exams. JEE Main exam, this year, will be conducted twice. Once in January 2019, and again in April 2019. For Science stream students who will be appearing for JEE Main too, pre-board exams can be a good opportunity to assess their preparation.
Pre-boards give the environment of a real exam. Usually, students get nervous during the exam and tend to forget information. This is why it's important to take pre-boards seriously, even if the marks don't count towards final result.
Treat your pre-board as seriously as your main exam, this will help you get rid of exam anxiety on the main day. After the pre-boards, identify your weaknesses from the results and work on making them your strengths.