It is important how much you know about a subject.
But what is more important is how much you know MORE than others.
You need to perform better than your peers.
Building up self-belief will help you to bolster your position in this critical period. Remind yourself of the things you do well and ensure that your positivity accompanies you till the end of the exam.
Start waking up on time and work towards a routine to ensure your body and mind gets adjusted to this pattern.
Revise as much as you can. Focus on all the concepts you have learned in the past two years. Questions in JEE-Advanced are more application based; so practice a lot of application-based and conceptual questions, possibly from mixed topics.
Even solving the last five years' papers will prove to be of great help!
At this stage, it is best to consolidate your position by working on your strengths rather than trying to take on your weak areas.
Do not try to attempt them as they will only confuse and frustrate you.
Temperament plays a vital role for success in IIT-JEE. Nervousness can decrease performance to a great extent.
Reach the centre at least an hour earlier or even before. Please check this out directly with the centre, leaving no room for mistakes. Keep time for travel, mode of transport and work out the details to the last tee!
To keep yourself cool against the scorching heat, wear comfortable cotton clothes.
Read the instructions well before answering any question.
For example, while attempting one question, don't think of any other question. This negatively impacts your speed while solving a certain question. Also, understand the question very clearly. Don't rush into solving it. Negative marking can severely impact your rank.
Instead, go in for a deterministic rather than probabilistic approach. Guess intelligently, if you must.
Do it after the exam gets over.