Just before you reach the isthmus between Lake Hāwea and Lake Wanaka on State Highway 6, take the turnoff on Meads Rd. This metal road can be a bit rough but gives you access to the north end of the lake. It crosses over steep, and incredibly green farmland below Sentinel Peak, then heads back to the lakeside and the Kidds Bush campground. The views from the high point on the road are magnificent, including the best view of Isthmus Peak and the isthmus itself.
You can continue for a while beyond Kidds Bush and the road eventually terminates as you head up the mostly northerly section of the lake towards the Hunter Valley. After that, be willing to tramp!
Watch out for the pretty unnamed waterfall as you cross a short bridge over one of the many streams that tumble down the hillside.