I know there are real 4x4 trails up there, but I don't know where. I've only gotten into wheeling in the past couple years so I'm not too familiar with them. You might want to look up the mammoth 4wheeling club over there. There are also some books that show the trails.

One of the nicest campgrounds is the one at Convict lake. It has private flush toilets (not stalls) and a lot of the camp spaces are surrounded by trees. The only problem is that it somewhat small and fills up quick so it's best to get there before the weekend crowd.

There is also a campground sort of near gull lake (in the June lake Loop) that I really like. It's called Reversed Creek Campground. It's kinda small but not too well known so getting a campsite is hit and miss for the weekend crowd. It has flush toilets and bear boxes. Take the southern entrance to the June Lake loop and keep going for about 3 miles. You'll see a small sign on the left that says Reversed Creek Campground. If you blink, you'll miss the sign.

Our old standby campgound is Oh! ridge at June lake. It's a big campground and I've always been able to get a campsite there, even at midnight on a friday (3day weekends excluded). There's no trees though and it can get windy at times, some sites have built in windbreaks. Flush toilets available.

There are more primative campgrounds at the obsidian dome and on tioga pass (before going up the grade). They have pit style toilets and no running water.

All the lakes in the area have campgrounds. I'd avoid the campgrounds in mammoth itself, they're the more popular ones where all the city people go. You'll have kids running around and people playing loud music.