One thing that struck my wife and I when we arrived was how alien the landscape was. It truly looked like another planet. First thing we did when we got into the park was to climb the nearest rock formation to get a better view.
A lot if not most of the campsites in the park are first-come first-served. We actually didn't find a campsite in the park the first night and had to settle for a site outside the park. I think we stayed at Joshua Tree Lake RV & Campground the first night on an exposed side of a dusky hill with a lot of other campers....not recommended if you can find a spot inside the park.
On our second day we headed to see if we could get lucky an open campsite at Jumbo Rock ( one of the best campsites imho). And we did, we got lucky and as we were driving in around 11am someone told us where they just pulled up stakes and we went straight to the site and got it.
If you go to Joshua Tree give yourself time to explore, I see a lot of people that never the leave the campsite. The park is huge and there are so many amazing hiking trails. Also if you can stay longer then a weekend you'll be glad you did.
A road dirt road that you should have 4-wheel drive for led to an abandoned mining shaft. Geology Tour Road was a cool, semi off the path loop that made you feel like you're getting away from it all.
If you like arches then you should make a point to stop by White Tank campground. The only arch in the park, but a nice one.
All in all it was a super fun little camping trip, I can't say enough about the park and how beautiful it is. One thing I know for sure is that I'll be back and just as eager to explore the amazing granite rock and trails.