You need your van to be level when you're camped. You'll sleep better, and your stuff won't go rolling away when you set it down. Most importantly, if you've got a refrigerator that runs on propane, you must have your camper very close to level, or you'll destroy your fridge.
RV supply outlets sell various devices to do the job. You can spend a lot of money if you want, but you don't have to. If you're slightly handy with tools, you can make your own leveling kit pretty cheaply.
You'll need a short level. Your hardware store probably sells little ones, 6 or 8 inches long. That will be accurate enough, but test it for accuracy before you trust your fridge to it.
If the bubble settles in a different place in the tube, the level isn't accurate, although you can still use it. You'll have to flip it end-for-end everytime and average out the difference in the two readings. As the Dead sings, the truth lies somewhere in between.
Next, make two ramps you can drive your camper up onto. I got the wood for mine, a few lengths of 2" by 10" laminated plank, for free from a contruction site's waste pile. The photos below should be all the inspiration you need. Cut your wood and nail it together to make the leveling ramps, each with two different heights.
When you pull into your camp site, set the parking brake, and put your level down on the floor. Test front-to-back and side-to-side. If the bubble is centered in the tube for both tests, you're already level. (Hey, it happens! Carry some champagne, just in case.) If the bubble is off-center, lift one end of the level, to see if that moves the bubble in the right direction. If it does, that's the side to put your levelers under.
You might need to raise both rear wheels, or both driver's side wheels, or maybe just a single wheel. Put one of your leveling ramps behind a tire, drive your van onto the wood, and test again. Play around until you've got it - maybe 10 minutes, once you're practiced up.
 
At Union Valley, I backed into the camp site I wanted and put the level down on GoGo's floor. The back end was low, so I put a leveler behind the right rear tire and backed up onto it. Then I checked the level again. The bubble settled mostly within the marks on the tube, so 2 inches was all GoGo needed. |
 
At Wrights Lake, the camp site had a steeper slope. I backed GoGo onto the first platform of the ramp and tested again with the level. He needed more height, so I backed up a little further, until the tire sat on the upper platform, almost 4 inches high. Very easy. |
 
If you need more than 4 inches, what you really need is a different camp site!