I'm in12th & want to do engineering from a reputed college. For this I've to clear mains.M not having any coaching.I want to know how to do?

personally i suggest you to concerntrate on the previous question papers.Plan well in managing the time. practice every day .I recommend you to concerntrate in mathematics as the assesment of two alike scored person is differentiated by maths score.Practice well.

ALL THE BEST

concentrate more on your PCM (physics chemistry and mathematics) and sole previous years JEE main papers

It depends on the syllabus you are currently in. If you are in CBSE, you are more prepared for the entrance exams. Your main focus should be on Physics Chemistry and Maths. For JEE Main or other engineering exams, those are the subjects that are important. I recommend that you shoulf stay focused on school work and make sure you are well caught up on that and are scoring well i school. Also, use the e books that this website provides. those will definitely help. Number 1 though: Do many many many past papers!!