How can I prepare jee mains 2018 in 3 months

If you have only 3 months left for the JEE mains to prepare then I would suggest only to practice the previous year papers of JEE mains which we can download from their official website or you can practice from the Arihant also.
Apart from that you should take good command on the books of NCERT of 11th and XII class and try to practice all the questions in the examples exercises and the miscellaneous exercises this would help you a lot.

If start planning and preparing from now for jee mains then you can definitely crack jee mains.Firstly i assume that you have got some basic concepts from ncert.Then try to analyse your strength and weakness.Try to improve your weak areas first by practicing questions.Solve previous years questions to get an idea of how the questions comes in jee mains and some questions are repeated also.Join online test series program of any good coaching institute.Dont waste yoir precious time now on social media. Be confident and calm while going to appear in jee mains.Be motivated!
All the best:)