Nothing special really.
As far as you as the seller go, its simply a case of collecting the money, signing and completing the sale declaration on the back of your certificate of registration, retaining the top half (notice of disposal) and either taking to the RTA, or completing the vehicle registration disposal notice online at www.rta.nsw.gov.au
The rest is up to the buyer to deal with, however as Chris mentioned above, it is a good idea to have a brief but detailed receipt of sale typed up in duplicate, with details on the car, the sale price, date, buyers details etc, with both copies then being signed by you and the buyer. I do this for every car I have sold as a record keeping precaution.