Your choices in your undergraduate studies will determine what learning areas you are eligible to apply for. Remember that you MUST have completed a major sequence in at least one of your learning areas at a tertiary level, and at least a minor sequence in a second learning area. If you meet the requirements for more than two learning areas, it is wise to consider several factors including employability (see question below), and the subjects or area you are most interested in and have the greatest depth of knowledge of.
Learning areas such as Mathematics, Science and English are very much in demand in Victorian schools, however you must ensure that you have the appropriate tertiary related experience before applying for these learning areas.
To help you make your decision, look at the content and outcomes listed for each of the learning area subjects in the University handbook. Keep in mind that certain learning areas are specific to either senior (years 11 &12) or junior school (years 7-10) only. It may be worth considering your employability across a school and selecting a combination of learning areas that allow you to teach across a range of year levels or across different disciplines.
For example, if you have an undergraduate degree in chemistry, you might apply to Science and Chemistry as your learning areas. The Science Learning Area will prepare you to teach science to students in years 7-10, where students study across biology, chemistry, Earth and space sciences and physics. The Chemistry Learning Area will prepare you to teach senior chemistry, a subject that available to students in years 11 and 12 studying their Victorian Certificate of Education (VCE).