Hi, I would like to know how much of an effort it takes to get into iit, how hard one must work and how many hours daily are sufficient.

        Depends on a person how well, he/she manages to study..

IIT-JEE preparation begins as early as 9th std itself.. and 11th std for some.

A complete focus on studies for 8hrs/day, (WITH breaks)

learning all the concepts , when a person still can..leaving no room for doubt or island if doubts.

Revising and re-revising the topic.

Maintaining a balanced diet and sleep .

KEEPING a prescribed Time table, to follow the daily routine..

         And in the end of the day feel confident about your preparation and your goal...

You can approve my answer ,below......

                                                                                                                                      Thank you, Yohann

                                                                                                                                         GOOD LUCK !!