Go to as many of the lectures in the first few weeks as possible, if only to meet your coursemates! Some are useful! (The first library session was pointless! The second wasn't!).
Depending on your department, you'll have to go to a certain building in Freshers Week to collect your Campus Card. (GO EARLY! Avoid the queues! Queued for 20 mins in one queue to only sit down for a second and confirm my name, I was then told to stand in another queue! For another 20 mins :/)
You should have a 2 hr session with your Tutor, and introduce yourself with your course mates. Meeting your tutor is very important! They will be the one writing your reference when you leave! (You might think - that's 3/4 years away! - If something comes up and you need to leave after Year 1 then you'll need a good reference!) They also have links to industries etc... They may also be your tutor for other units, so you could potentially be seeing them for 4 hours a week!
Take a planner/Diary to this. You will get a lot of different dates over late September/October for submission deadlines, Oral exams etc...BE ORGANISED!
You should have a lecture session for each unit you do, these will probably not last the entire hour, they will go over what you are learning, what they expect from you and your exams...
You will be given A LOT of paper, buy a folder and a hole punch! You will have a handbook for each Unit, so no point in writing down dates of exams until closer to the time
My top tip is to be organised, from the very beginning, keep on top of reading, outside work etc... and you will find the looming deadlines not too scary!