There are a number of walking options in the Royal National Park that take in a section of the classic 30km Coast Track. One good option is to start at the Garrawarra Farm car park on top of the escarpment, walk east down Burgh Ridge towards the sea, then walk north as far as Garie North Head for excellent views back down the coast. And in the summer holidays Garie Beach is patrolled so you can safely have a swim before heading back.
To park at the Garrawarra Farm car park you have to pay the RNP entrance fee. Follow the walking track east down Burgh Ridge, and towards the bottom take a left turn onto the Coast Track, walking north-east towards Era Beach. (Most others will turn right towards Burning Palms and Figure of Eight Pool). You can turn around anywhere you like, but I think it’s worth walking to Garie Beach and then climbing up Garie North Head for great views back down the coast; when you reach the top you should take an indistinct foot pad to the right to reach the cliff’s edge. Return the way you came, or maybe someone can pick you up at Garie Beach.