Well,I am a student of IIT Delhi in the comp sc branch.
I qualified the jee 2005 with AIR 56 in mains and AIR 22 in screening.

As far as my experience was concerned,it was very enjoyable.

No

doubt,the syllabus and the jee itself is not the easiest,but if you work hard in the beginning,it is possible to develop the analytical skills to clear jee very comfortably with a good rank.

I started studying from 11 class itself and fully utilized the 2 years.
It helps if you cam bunk school so that you can not only devote enough time for the jee prep but also find some time for enjoyment -which will recharge your batteries for the day ahead as well.

Dont delay the start of your prep as the more time you have ,the smooother you can pursue the completion of your syllabus.

Do join a good coaching center as it gives you the necessary motivation to spend your time preparin for the jee.Once you get started ,the onus is on you to carry on the momentum.

The center I had joined had very bright students who were NTSE scholars(I kind of felt very average).But very soon ,I was scoring two-three times of what they were scoring in mock tests and quizzes.

As far as the books are concerned,I used the following and would recommend the same to you:

Physics:
Start with HC Verma in class 11,and of course your study package.If you find HC Verma too simple,you can leave it and start with fiitjee study packages.But it is a good idea to complete part 1 of this book in class 11.

In class 12,you cam start seeing other books,if you feel confident that HC Verma is too easy for you,start with DC Pandey (problem book) from Arihant Publications.The questions are a bit tough so its ok if you can solve 50% of the problems.If you want to score well in screening,read the ncert once(which you would be for your boards anyway).I dont think there is a need for Irodov.Fiitjee?s GMP is also a good idea (only after you have revised your syllabus to your satisfaction).

Chemistry:
Again ,the study packages are important.
Physical--P.Bahadur
Organic--Study packages,previous year papers,practice problems at the end of P.Bahadur
Inorganic--NCERT,Study packages,practice from P.Bahadur and any other problem you can find(focus on 3d series )

Going thru NCERT is very important!

Maths:
Well,besides study packages,TMH is the best book.But it is not everyone?s cup of tea!
If you find it impossible to crack even 20% of problems,refer to prevoious years papers and study material of some other institute.You can start with the book in class 12.
Solve it completely and 90% on your own,you are ready for any question!

Total:
1.Do join a good test series(Fiitjee is the best I think)
2.Completely solve previous year papers under strict time limit and honestly evaluate yourself.
3.Test yourself right from class 11 and work on improving your scores regularly.
4.Read the questions very carefully.The questions are tailor made for silly mistakes.
5.Concentrate on scoring a specified amount of marks if you find the paper difficult(dont expect 170/180!).

Conclusion:
The top ranker usually has a score of 140-150 that is about 80%.
If you completely avoid silly mistakes,it is very easy to get a top 500 rank and with good effort you can get into top 100 or 50.

No one scores spectacularly in all 3 subjects (AIR 21 has 28/60 in maths jee 2005!)
Hence concentrate on consistency in all subjects.

Most importantly,stay cool on the day of exam.
Think that you have nothing to lose.

Everyone else is under a lot of stress,make full use of this.
Under a situation of no pressure,your performance will increase drastically.
Dont get unduly affected by the standard of the paper,it is the same for everyone.

Once you get into IIT,you still have to work hard at times,but not only is life very enjoyable,but your future has no limit as far as your success is concerned.

Good Luck.And remember, a job enjoyed will always be a job well done!