Start at Donner Lake. It sits right in town at the foot of Donner Pass, warm enough to swim off the east-shore beach through July, and you can camp a short walk from the water in the lodgepole pines at Donner Memorial State Park. The season is the catch. The campground opens in late May and closes around mid-September, weather permitting per California State Parks, and the sites go on ReserveCalifornia six months out on a rolling window. Book the site first and the van second. The van is the easier half to find.
The lake is the whole point, an easy swim-and-paddle shoreline with a beach at either end. At the day-use end the Pioneer Monument stands over the picnic tables, its granite pedestal facing the pass and the emigrant party that got caught here the winter of 1846. This is black-bear country, so food, toiletries, and any cooler live in the steel locker at your site, day and night.
The west shore of Lake Tahoe
From Truckee, CA-89 runs south along the Truckee River to Tahoe City, and the big lake opens up. Ed Z'berg Sugar Pine Point State Park, further down the west shore, is the overnight that actually sits on Tahoe, pine and cedar running to the water. It takes longer vans than Tahoe City's own campground does, and its loop keeps running after Donner shuts for the year, which is why winter trips end up here. That in-town camp, Tahoe State Recreation Area, is a tiny lakefront loop of small historic pads better suited to a short rig, and it books through ReserveCalifornia.
Palisades Tahoe
Palisades Tahoe sits up Olympic Valley Road off CA-89, and it is why Truckee runs on a ski calendar. The valley hosted the 1960 Winter Olympics, and the combined complex is the largest in the Tahoe region, with the granite palisades themselves standing over the base area. Nobody camps at the resort. In winter that means sleeping on the west shore and driving in, and in summer it flips to a tram ride and a hike. Either way it is a day, not a night.
Emerald Bay and Vikingsholm
Keep going south on CA-89 and the road climbs above Emerald Bay, a granite horseshoe of blue-green water with Fannette Island alone in the middle and a small stone tea house on top of it. Build a day around it rather than a night. The lot at the bay turns away most campervans on length, so the realistic version is the highway overlook, a walk down only if your van is short enough, and then back up the west shore to sleep. D.L. Bliss sits a couple of miles north under the same rule, which folds it into the same day. If your group needs more beds or more length than these state-park lots allow, RV rentals in Truckee cover the bigger rigs, with the same Donner and Emerald Bay limits still in play.
Yosemite is a longer haul south and gets its own base at campervan rentals near Yosemite. For other starting points around the state, browse campervan rentals across California.