Without a four wheel alignment machine there is no real way to dial in that I knew of..SO
Promise you wont laugh. What I did was to take some 1 X 1 square tubing and use some 6 foot long sticks of it I had in the shop. Strapped them to the outside of the rear tires and let them run down alongside the Jeep.
As the JK sort of bulges out in the middle (like me) and then is pinched tighter in the front end, it can be real fun to tell much, but you get the picture.
Also don't be mislead by the fact that as you go up in height, your axel will stick out more to one side.
What you are looking for in this Hillbilly example is to see if the tubes are kicked one way or the other.
I did not need to dial it in much of at all. Just made sure all arms were the same side to side and set your rear pinion pointing up in line with the driveshaft.
This tube strapped to the tire also worked good in the front to get me in the ballpark. I still had the ESC come on and freaked out over that. Thanks to the help of Overlander and some others on here it was a short lived deal once I got the steering wheel strait it went off in about 1/4 mile.