Start by stating the relationship between parliament and the courts; e.g. parliament creates court, courts interpret legislation, parliament may incorporate common law principles etc.
I would also include how the courts make law through the doctrine of precedent, and the circumstances (and limitations) of this, include an example, such as the Donoghue v. Stevenson Case.
Compare common law to parliament who are not subject to such limitations, but explain the strengths of it over parliamentary legislation.
If you like you could expand on the codification of common law in parliamentary legislation, again include an example (e.g. the Mabo Case)
Finish by summing up your points with a final evaluation of its strengths and primary weaknesses. Here I would do a final assessment of "and should continue to do so"