If you're just doing just commerce:
Semester 1:
4 compulsory courses (Acct 1a, micro, BES, MGMT)
Semester 2:
Choose 4 elective level 1 courses (there's a list on the UNSW website)
If you know which majors you want to do, then choose the corresponding elective coruses for that major cos they will be prerequisites (part of the major)
You choose your majors in 2nd year. Even then, you can still change your major later anyway. If you've done courses in your old major that are not part of your new proposed major, they will still be counted into your commerce degree (not major). You have up to 3 courses (18 UOCS) that can be counted as "extra courses from the ASB) - "see flexible options"