JEE

Your first preference should be to concentrate on 11th and 12th examinations (without which all your efforts might become futile).
Parallel to that you can start preparing for the joint entrance examination (JEE), by following meticulously the following steps:
* Have at least four to five years' question papers of JEE, so that you will get to know about the pattern.
* Start preparing seriously the objective types as well as descriptive types.
* Try to make "your own style, precise, notes", which will help you get the glimpses very fast.
* Start preparing seriously analytical portions followed by theoretical portions (this approach will help absorb the concepts in a better way).
* Start answering them in the stipulated time, so that you have a sort of rehearsal.
* Avoid late night preparation (choose early in the morning time).
* Avoid spicy food as well as junk food.