before you start. think of what you are going to major in. you can have a look of the units required for each major and a suggest course progression map here http://www.buseco.monash.edu.my/for/current-students.html

if you are not doing majors that require certain 1st yr unit, you can always do those 1st yr unit later on. to balance up the work load of 2nd and 3rd yr units.

and do check whether the units of your major are offered in both semester, or only in s1 or s2.