Firstly, it is good to know that the IIts have attracted Indian students from the middle east. I congratulate you upon starting this educating journey of IIT preparation. The next four years of your life will determine where you ultimately and where you stand.
Most Indian students slog in their youth. IITs are the dream of almost every Indian. For those of you who favor MIT, Caltach etc. , the IITs leave them in the dust in science and technology. True, the education isnt well rounded; nobody majors in music, but their existance from ~ 1950 revolutionized Indian brains. Being a mechanical engineering graduate from IIT Delhi or a computer geek from IIT Kanpur sure means youre brilliant. Remember, it isnt easy to reject an IIT graduate.
Lets cut to the chase. Preparing for the IIT (IITJEE) means you are taking time off from school to focus and strengthen P, C and M. There are only 3 subjects. Studying for this exam automatically prepares you for international olympiads like the INChO, IPhO, IMO, RMO and many more. Regarding when to start preparing, anytime from eight is advised. In the past, most students just neede a their twelth for preparation. Now even four years cant guarantee a seat. For 2013, there are two components: Board exam result and JEE questions. My advice would be to join the best preparation classes.
Hope you make it!
Varun (I study the IGCSE to. Im in eighth grade and also an IITJEE aspirant)