Hiya, first of all stop stressing, at the moment all you need to do is plan your timetable so that when you go into uni and get your academic advice/enrol it will be a quick and easy affair and you'll hopefully get the tutorial times you want. No one (not even continuing students) has actually picked classes yet, so all the good spots haven't been taken at all.
I'm not sure at what stage this happens but you should have/will received a date and time to go into uni for academic advice and enrolment. Pretty much what happens is that you go in and have your timetable checked by an academic adviser (to make sure your not taking anything your not supposed to) and then you will be taken to a computer lab where someone will help you actually enrol into the units and class times that you picked. So what you want to do is have your preferred time table ready to go so you can get it checked out and get enrolled nice and quickly, some people show up on the day without having done this and end up spending hours at uni figuring out what to do.
If you look up your degree in the hand book you'll see all the requirements:
http://www.handbook.mq.edu.au/2012/...+Commerce+with+the+degree+of+Bachelor+of+Laws
As a first year student, you should be taking 100 level units. So pretty much, have a look at the 100 level units in the above link and pick ones that you like. Most students will take 4 units a semester, but if you want to do less that's fine (i personally only do 3 a semester, this is the minimum you can do and still be considered a full time student, less then 3 and you're part time), you need to make sure that the units you pick are evenly spaced across two semesters. You can see if a unit runs in semester 1 or semester 2 by by clicking on the unit code in the above link and looking at 'When offered'. For example ACST101 says 'D1 - Day; Offered in Session 1, North Ryde', so it's offered in semester 1. You need to pick 4 100lvl units for semester 1 and 4 100lvl units for semester 2.
Once you have picked your units, go to the timetable site:
https://timetables.mq.edu.au/2012/
Here you simply pick the relevant semester (to the left of the page, either session 1 or session 2) enter the code of your unit, enter the time (for you just say 'all week') and the type of format you want the timetable (i think 'grid' is easiest to understand). Then you can see the times of the lectures and tutorials and pick your preferred times. To know exactly what you need to be picking, above the grid it says 'This unit has a teaching structure of ....'. Say it says 'This unit has a teaching structure of Lecture_1 and Tutorial_1', this means you need to pick one lecture time and one tutorial time (it's best to to pick a tutorial time after your lecture). Since the timetable maker only lets you do one unit at a time it can be a good idea to have excel open or something to note down your preferred times as you go through each unit.
This is just general advice on how to pick units and make a timetable, i don't really know anything about your degree, so maybe someone else can help you out with what the best units to take might be. Remember, even if you screw your timetable up someone will help you sort it out when you go in for academic advice/enrolment.