If you find yourself in Xining and looking for an adventure, skip Qinghai Lake and go to Kanbula Forest Park. (I mean, or go to Qinghai Lake too, just be sure to rent a car and don't take the bus. Kanbula's easier to have a good time in, if you're by yourself.) This post will attempt to cover all the nuts and bolts to help you get there, because I couldn't find a lot of great English info when I was looking. It's oriented to people googling for Kanbula (or Zhakanbula, or Khambra, as it's also called) - hello googlers! if you have any questions, please leave comments.
Getting there: take a bus to Kanbula from Xining's coach station (right next to the train station). Cost me ¥22.5, and left at 10:30 AM, with other options throughout the day, at 12:00PM and I think 1:30 and maybe another one too? Took about 2.5 hours. The bus arrives in Kanbula town, and a bunch of drivers had vans to take us the last couple of km to the entrance to Kanbula park, for ¥10 each.
Getting back: I don't know exactly when buses go back to Xining. One person told me 10am, one person told me 12:30pm, one told me 11:30am. Who knows, they may all be right. At any rate, it's possible to get back. I think you can also get back the same day, but you should spend a night, it's more fun.
Where are things: the park is around the Lijia reservoir. There's one road that goes around the whole thing. The entrance is at about four o'clock. There are free buses that will take you around this road, counterclockwise usually, and stop at tourist viewpoint sites. There's also a boat that goes across the reservoir (also free); catch it at the first bus stop (around one o'clock on the map) and it takes you near Nanzong monastery (which is in the middle of the clock). That's the route I went: on the bus from four o'clock to one o'clock, took the bus to the center, then walked to Dehong at about seven o'clock, then eventually got a ride back to the entrance and out of the park. So I don't know what's in the western half.
Sleeping: there are some guesthouses in the villages along the south side of the road around the park. I stayed in Dehong, with a Tibetan guy who approached me along the way, for ¥70 including dinner and breakfast. Basic (outhouse etc) but it was fine for a night. There are guesthouses too that I think are a little nicer for about ¥100. Other travelers around the internet report staying in the Nanzong nunnery, but I didn't try; didn't want to impose on them.
Food and drinks: not a ton. Bus stop #1 (at one o'clock) has instant noodles and stuff, and the boat dock has people cooking bread, potatoes, and eggs. Supposedly there's a restaurant in Dehong; I got dinner and breakfast from the folks I stayed with. There are a lot of places you can buy water and non-perishable junk food though.
What to do: you _could_ just take the bus and boat around and take photos at all the tourist sites. Luckily, you can also get off the path by just getting off the bus and walking somewhere. I can't really recommend hiking routes because I didn't have a map, though some other people did so there must be one somewhere (maybe Chinese only). You can hike up to Nanzong town and monastery, and nearby there is also a wooden stairs thing that goes up to a very high place. Shoot, there's viewpoints all over the place. You'll get some good pictures however you go.
Cost: ¥240 to enter the park, as of 2016. (oof!) But only ¥22 for the bus each way, and ¥70-100 to stay the night. Plus a few bucks for food and drinks, and you've got a two-day trip for ¥400-450 per person. Not super cheap, but you could do worse, and it's worth it.
Why's it worth it: I mean, mostly great views. You get the red rocky mountains, the high altitude lake, and some nice forests. It's not super touristed; it is a little bit, and will undoubtedly get more, but you can still get off the path a bit. (as opposed to, say, Qinghai Lake.)