Go in small steps... I found its trial and error doing it on the truck. Between the three 2nd gens I've done, and now my 3rd gen; I have yet to go much more than a single turn on the adjustment... don't get crazy.
I do it with the front tires off the ground, and physically turn the wheels left and right by pushing and pulling on the tires (steering wheel unlocked obviously) to get a feel. . you will start and the wheels will turn easily, as you adjust, they get "stiffer", too much and they get "sticky" near center. This is done at the axle, not by the steering wheel.
When done, the steering wheel should go from sloppy/loose to somewhat tight/firm. And again, too much and the steering wheel will feel sticky... and during a test drive, the steering will only return part way and "stick" before going center. If the steering won't return to center by itself, then you are too tight.
It doesn't take a lot of adjustment to make a big change... again, don't go crazy.
Just for the record, I did the first two on the ground, it took me about 4 hours of adjust, drive, adjust, drive, adjust, drive to get it right... doing it on the stands takes under 30 minutes. Be patient and don't go too tight... and you do "tighten" the adjustment screw to take of the slack... but the screw never actually feels tight when you adjust it. I have never adjusted one by following the FSM directions.
I can actually leave go of the wheel at speed now and the truck tracks straight and true for as long as I have straight road (even with uneven tracks and bumps)... before I would have been chasing it constantly.