The "approach" begins at the Maroon-Crater Lake trailhead located on the east end of Maroon Lake. Watch for a registration station to obtain an overnight backpacking permit. Also plan on being required to have a bear-proof canister for food storage. The trail goes along the western shore of Maroon Lake amid the hordes of daily tourists. Many of these will make the hike to Crater Lake. This very-well-worn trail climbs steadily to Crater Lake passing the wilderness boundary (though you likely won't feel like you're in wilderness until you get beyond Crater Lake) along the way. It passes through a terminal moraine area before arriving at the lake and the trail comes to a junction near the lake on the northern end. The right fork leads up Minnehaha Creek to Buckskin Pass. For this approach however, you'll continue south on the trail that skirts the west side of Crater Lake and continues south to West Maroon Pass. There are designated campsites in the vicinity of Crater Lake.
As you continue up the trail, there is an area not too far south of the lake where the trail gains about 100 vertical feet, then loses that elevation as it crosses an area of talus. The trail also cuts through numerous areas of willows, which when laden with rain drops and drooping over the trail, will provide a nuisance of a shower as you pack through. At about the 3.75 mile point, the trail crosses from the west to the east side of the creek. A little before that crossing, you may spot some suitable campsites that we used in 1993, on the same side of the creek as the trail. More sites exists after the creek crossing, about a half mile past at the most. Basically, you want to camp somewhere near where the access is to the somewhat hidden basin below Lightening Pyramid and UN13,631B. Camping here will make it possible to reach all three summits in a day as we did or will at least make getting all three summits in two days easily possible.
There are designated backcountry campsites at Crater Lake. Beyond there, as you proceed south up the creek, there will be other primitive site opportunities, if the White River National Forest is still allowing at-large camping. Check the most current regulations before making any assumptions. Over the last couple years, White River national Forest has moved in the direction of imposing a number of new camping and backpacking regulations on this area. The following coordinates are a "best guess" as to where we found a place to camp in 1993.