what should be the main target in 12th.to get good result in 12 class or to prepare for IIT???

you have to score well in 12th exam and also your preparation should be such that you should crack IIT-JEE.for this you have to study well with some best books for each subject and also you should take online classes, spped test etc.

Making good % in class 12 is very important, and if you want to join an good IIT institute you should be focussed, persiverant .Besides this both the things can go together as a good study material provide you to acheive both the targets.Join a reputed coaching can also be a good choice.
Thanks & Regards
Aarti Gupta
askiitians Faculty