First of all, welcome to your new home, freshers!!!! Let's come to the point. I know many of you would be disheartened with your jee rank & might not be satisfied with the branch. But, let me tell you something. Bear in mind, no branch is bad if you excel in it. At the end of four/five years, all that matters is what you learnt, irrespective of your branch. Still, if you want a department change or "dep-c", all you need to know is that make your acads your priority. Attend the classes. Even the boring blabber of some profs bear some importance. The labs are excellent and try to learn as much as you can there. Don't leave the lab reports to be completed for the last minute. I suggest don't copy lab reports from dc. Do some research ("google"), that will help you in viva. Try to solve previous year question papers before exams. Even after doing this, you'll have plenty of time for co-curricular activities and "bhaat" sessions.
Most importantly, enjoy your first year because you will not regain your fachchhapan, ever."