There’s just one “strategy”!
Study like you are studying to save lives one day. Put in your everything.
Get your concepts cleared and revise the ncert minimum 10 times. You must memorise each and every line ( chem and bio ). For physics, memories the formulas and practice minimum 100 MCQs from each chapter ( you can refer to DC Pandey for that ). Take a LOT of tests. You can join Allen / Akash for the test series or you can downloaded papers online. Analyse your result and work on your weak topics. You’ll be good to go !