There are coloured arrows that shows what happens when you increase or decrease a parameter, and a description at the bottom what the colours of the arrows represent.
For example: Spring rate front
Decrease:
Decrease tire wear
Increase grip
More oversteer
Increase:
Increase tire wear
Decrease grip
More understeer
If the car has a tendency to oversteer you can either stiffen up the front springs or soften the rear springs.
Or you could also add negative camber to the rear wheels, helps a bit in cornering stability.
Here's site I have bookmarked.
http://www.rapid-racer.com/suspension-tuning.php