I personally use both math and trial and error.
Take height and springs for example. "In my theory", every car has a spot that it like the most. And the car keeps getting better and better, grip and more grip, until it hits that spot, then whoosh, 5 points too low and the whole things junk.
I believe that much, we all kind of believe to be true.
As far as math goes, I start out at 75% height, and test 25%_50%_75% springs on it.
Then depending on the average of those 3, try either 65% or 80% height! with the three springs.
When I find the height I like the most, I try the three springs yet again, only 9 configs. (25%f/25%b, 25%f/50%b, 25%f/75%b, 50%f/50%b, 50%f/25%b, 50%f/75%b, 75%f/25%b, 75%f/50%b, 75%f,75%b)
That part is tedious. But the math is exact.
This isn't how I started out doing it, this is what I've come to. This is what I've found to work best, out of all the methods I've read and tried, in what, a month since Christmas when I got the game, lol?
All this, understand, I don't even touch anything on that section of the car, until after I have the 'initial' LSD settings done.
I run the LSD tests first when the car is stock. Make my changes, THEN I do the height and all that, then I revisit the LSD when I'm done.
But I am under the philosophy, that my method works for me, but not everyone. And the game is so new, that there is a lot we all don't know yet. So yeah, I'm very interested on how others do this. I'm forever learning and growing, or try to be anyway.
. Room settings don't lie though 
