University is not like high school, you have a lot more freedom and are treated like adults, after all you will be studying with many adults. Obvioulsly etiquet is advised when it comes to mobile phones, use them as if you would in a cinema (keep them on silent, if you need to make/answer a phone call then wait for an interval or walk out quietly). As far as being 'on campus' you can more-or-less do as you wish, within the law.
The main thing is to listen to when the assignments are due, mark it in your calendar and complete them by the due date, you will not get lecturers and tutors on your back telling you to do your assignments, or making you stay behind after class if you don't, they will just mark you down or fail you if they are late!
Don't stress though, these are the best years of your life!
