Lake Ozette is in the upper NW corner of the Olympic Peninsula. The lake is 14 miles long with several bays and a few islands. On my last trip the lake was calm as could be, but the lake is only two miles from the ocean, so the possibility of big wind and storm is always there.
A NPS wilderness permit is required ($13), which can be picked up in person at HQ in Forks or Port Angeles. There are several preferred campsites, but you can camp on any open ground except for the few remaining private properties.
There is one maintained trail near Ericson's Bay to access the ocean and one gnarly unmaintained trail at Allen's Bay to reach a much more remote stretch of beach (see a USGS topo for that one). Bear Cans required.
Unlike those big reservoirs in this state, you can beach a boat on almost every inch of the shoreline if you have to.
NPS Campground at Northernmost point of lake. Other campsites are primitive. Most people launch at Swan Bay, parking there is free.
Wilderness permit ($13) required.
Bear cans required. NPS rents bear cans.
The Ranger in Forks or Port Angeles will give you a park map which shows all of the roads. There aren't many roads to choose from. It's all paved except the last half mile to Swan Bay. The only other road to reach the lake is at the north end campground.
National Park Service
USGS topo for the area is as good as anyone needs.