It is a good idea to start this from the top at Station Rock end. Unless you really like steep hills. :)
Station Rock track is a fairly new track. Originally it only went up to Station Rock but now it has been extended. It follows along the ridge-line to meet Kowhai Valley Track. This means you can do a nice loop by walking up the Medlands Hill, along Station Rock, and then drop down Kowhai Valley track back onto Medlands Beach.
The track up to Station Rock is good. The next part of the track is brand new and well marked but it can be muddy and slippery. When you get to the Station Rock turn off, maybe 15 mins in, it is worth going to have a look at the view. Looking west you can see down the valley to Medlands. And looking east you get a good view of Tryphena and Coromandel.
You can also see one of the radio masts for Aotea FM.
After going back to the turnoff you can head south along the ridge line. I was a little disappointed in the views but perhaps that was because I had seen them before. It is really more of a nice walk in the bush. A lot of work has been put into the track but unfortunately the pigs have decided it was all for them.
Kowhai Valley Track
Kowhai Valley Track runs from Rosalie Bay road down to Medlands Beach. Station Rock track joins on about 200m down from the road. If you have the time go up and have a look if John Kargaards gallery. Otherwise it is downhill for quite a way. There is a seat near the bottom of the incline and then you go through some coastal forest before coming out onto Primrose Road at Medlands.