I'm sure I overthink it, but I have two methods. One is when camping, it goes like what most are saying above.
1. level side to side.
2. install X-chocks.
3. unhitch and level front to back.
There are no traditional wheel chocks used in this process.
At home, I do it a little different.
1. level side to side.
2. block the wheels with normal wheel chocks.
3. unhook and level front to back.
4. install X-chocks.
I do this at home just to make sure the wheels/suspension are not loaded by the chocks. I don't really care for a weekend camping, but if the trailer will be sitting for an extended time I'd rather have everything settled before locking the wheels tight.
But that's probably just me over thinking it. :B