Profs won’t come after you for missing assignments. If you choose not to submit your work, that’s your prerogative but don’t expect to be able to turn it in at the end of the term and get credit for it. It is your responsibility to get your assignment in on time, if you don’t, it just means one less thing for your prof to mark.
You don’t have to ask to go to the bathroom. It may sound silly, but you don’t have to sit in silent agony with your legs crossed waiting for class to finish. You can just get up and go – but make sure to leave without disturbing your classmates.
The majority of learning happens outside of the classroom. Participating in research labs or having discussions over a beverage is where the information sinks in. Don’t be afraid to invite your classmates out to chat about things.
In university you have to schedule time with your profs. Your professors want you to come see them, but they also likely have research commitments as well as hundreds of students, as opposed to 30 like in high school. Book an appointment to meet with them (they’d love you to), because you won’t be able to chat with them for 45 minutes right after class when there’s a line up of other students with questions.
Your classes will almost always be in different buildings – this means potentially long walks in between class (with an 85% chance that it will be raining). You also don’t get assigned a locker so you have to carry your life with you!