I hope that all of you are all boosted up with confidence and ready for the part where you need to prove yourself. If in case you are not, then don't worry because I will tell you the areas you need to work on so that you feel ready for the competetion.
Let me tell you that I appeared for JEE two times. I cracked it both the times but believe me that there was a huge difference in my temperament when I think of both times. I will tell you what you must do and things that you should avoid.
Exams are meant to be cracked - Let me tell you that if you have prepared well then there is no need to worry. Any exam is good only if right people(those who were sincere in there efforts while preparing) can get through it and JEE is one of the best. So, make sure that you understand that those are the real people who will get through JEE and you are going to be amongst them.
Believe in your preparation and yourself - People, you got to believe in all the hard work that you did. Remember your late night or early morning studies, remember the feeling you got when you solved a very long Maths question or a tricky Physics one or when you were able to remember those exceptions in Chemistry. Remember them and credit yourself for it and trust me if you could do it once then you can do it on that day too.
Revise but refrain from starting new topics - You should go through all the concepts and formulas that you have studied at least once in these days. However, don't even think of beginning anything new because you may not be able to complete it or find it difficult and that may lead your confidence to plummet.
Solve question papers - I hope that you are already giving atleast two 3 hour test everyday. If not, then do so and try to reduce those silly mistakes. However, don't do this drill on last day before the exam. On that day, just relax.
Be healthy - Don't indulge yourself in bad eating habits i.e. any fast food or anything from outside. Eat every thing cooked at home. Start sleeping well and make your biological clock as you would want on the day of exam i.e. avoid sleeping in afternoon (it is hard as summer is approaching), strict beakfast and lunch time, etc.
Avoid people - Yes, you read it right. Avoid people to talk with you on JEE subject(it can really be hard given the moment but try). Talk only to those who motivate you and avoid those who find faults in you. Be only with your family and teachers and avoid friends for a while.
Keep calm and be focussed- Whatever be the scenario in this world, it always comes to holding one's nerves at the end in order to be successful. JEE is no different. Make sure you don't get irritated or distracted because of small things like condition of your exam center or a beautiful girl sitting in front of you and so on. Take a deep breath and attempt the question according to your strength areas and in a way that saves time.
e.g. I was very confident in Physics and I took less time in Chemistry to solve questions I know, so I used to attempt Physics followed by chemistry and then give the saved time to solve long Maths questions in case value putting doesn't work. That was my paper solving strategy and you may have one of your own which can be totally different.
Finally, I would say that just hope for the best and you will get whatever is best for you. Hope that above tips help you to get through the exam.
At last, All the best to you all.