You generally won't have academic subject lectures in the first week, which will be Fresher's or Induction Week. The uni will usually send out a timetable of events.
You'll probably have at least one session in a lecture theatre, which introduces you to the teaching staff, the campus etc. This type of 'Welcome' lecture is pretty standard. You may also have things like a guided tour of the library to show you things like where the bulk of your subject books/journals can be found, how to check books in/out, how to access ebooks/ejournals etc. Take a notebook and pen for this type of activity, as they'll be giving out useful info, but don't worry about a laptop. If you need to sign up to anything online and you can't get to a uni PC, you can always do this off campus, later in the day.
Freshers' Fair is just a matter of wandering around the various stalls, gathering handouts and freebies. I'd definitely recommend having a bag with spare room for carrying that lot about, although you may get a free bag with some of the handouts. A notebook and pen might also come in handy, but usually clubs and societies will have handouts with their contact details on them. Some clubs have a membership fee, but should let you sign up at a later date so you can decide whether you really want to join. At my current uni, all membership fees have to be paid online so you usually can't join anything other than the mailing list on the actual day.
You normally have to formally enrol or register at uni during your first week. You'll get an email or letter from the uni telling you where to go on campus, the date/time and what you need to take. For my enrolment, I had to take my offer letter and A Level certificates, so expect to carry things like that - you'll need a waterproof bag, big enough to get official A4 documents in it without being folded or damaged.
Bring enough money to buy coffee/lunch, or carry a packed lunch if you prefer. Nobody will mind you sitting in coffee, bar or restaurant areas if you bring your own food and drink.