First know the entire syllabus. Then make a proper and programmatic study schedule which you'll follow throughout your preparation . Most of the students don't make a proper routine and study abruptly. Instead of choosing a random topic from the syllabus, you must break your preparation into sections. Sub-topics from each section should be selected and then strategy on clearing concepts must be made. Never leave any concepts doubtful or unsolved . Try to make your own notes. This will help you in revision. Once done with the syllabus and concept clarity, you should move towards solving previous years papers. Give mock tests as much as possible. Time management is one more important thing you should look upon . Many students don't look at the time while solving previous papers or mock tests at home. You should focus on this. Remember that practise will increase your efficiency. Get the best books for preparation. NCERT Textbooks of class 11 and 12 are best for basic preparation and concept clarification. Don't go for a huge amount of books for preparation. You'll be messed up . Once done with this, you can move on to other books. Try to give one mock test in every week so that you can understand where you're standing.
Go through these-
http://engineering.careers360.com/articles/how-prepare-for-jee-main
http://engineering.careers360.com/articles/jee-main-question-papers