Honestly, since you're going into first year, you should get into all the classes you want since they're so big and there really isn't that much selection in terms of electives in first year. Although some classes fill up quickly (i.e Microeconomics) so you should have 1-2 back-up classes anyways. But the only thing that might concern you is not getting into the core/tutorial/lab time slot you want. So i would also come up with at least one back-up time slot for each of your lectures, tutorials and labs for all your courses. Hopefully this helps somewhat