The approach for JEE is a methodology prepared to suit the self and the paper, honed over tons of practice tests and given the fact that it is purely personal, I would share my methods and the way I had given it a shot.
E-M-T Approach – Easy, Moderate and Tough is the method. It indeed mirrors its literal perspective but also follows up on a few time bound steps. Go through the whole of the question paper at first in the initial 5 minutes. This is very necessary as it gives you a complete idea of the level of the question paper and helps you decide on the questions to ‘attack’ on first. Do not leave this step at any cost!
Given that you have gone through the questions initially, go through the ‘easy’ questions first, and mostly start with Chemistry and Physics. In this step, you need to go through the Inorganic and Organic Chemistry, and theoretical questions of Physics, and have it completed at the earliest, like in 15-20 minutes. The next step should be giving Mathematics the first shot for another 30 minutes, with the basic and easy seeming questions covered.
Thus, by the end of the first hour you have around 30-40% of marks under your sleeve and you are good to go for the next half of the paper. Now, come to the moderate questions and give them a cool amount of time in the same order – Chemistry, Physics and Mathematics giving 15 minutes, 30 minutes and 45 minutes respectively. Having given time as stated, you are left with 30 minutes at the end of the planned schedule.
Now, the last period may be given to the toughest of questions, accounting for 10% of marks, or to review the marked ones that need to be done again or confirmed. Further, do not try to complete the paper, but be highly selective and do the best to score the maximum.