Sample Papers - Class 12

Sample Paper 1
Sample Paper 2
Sample Paper 3

Learn all definitions along with their units and dimensions ( e.g. define electric field intensity, ampere, mutual inductance, temperature coeff. of resistance, magnetic susceptibility etc etc ... )
Draw and practice all diagrams ( e.g. - Cyclotron , galvanometer, microscope, amplifier etc etc ... )
Write and learn all derivations / proofs again and again and again until you are confident.....
Read the textbook very seriously and get the concepts clear. Very useful for solving application based questions.
Solve more and more numericals within your timeframe. If you are screwed while solving a numerical problem during the exam, don't keep on scratching your head, but move to the next question and attempt the numerical later.
Write / Solve previous year / sample papers, atleast three after each revision. You should revise the full course atleast thrice before your board exam starts.
Respect your two-wheeler and avoid un-necessary travel.
Finally, Sleep well, Eat well and Relax. You are going to an examination hall, not to a war zone. Hope for the best but prepare for the worst.