I prepared for JEE at FIITJEE Kalu Sarai. All I'd like to tell my juniors is that you should be prepared for the long haul. Two years of preparation may sound easy, but it is a long road paved with great challenges.
Do not burn yourself out in the first year if preparation itself. Many of my friends were studying 10-12 hours a day daily in class XI and ended up running out of steam when it mattered the most. Time your preparation to perfection and don't study just to make up the hours. If you study spend 12 hrs trying to finish 3 topics and end up completing none of them, the dozen hours of study make no difference. If you instead invest 3-6 hours on one single topic and finish it, it is still time spent in a better way.