There is a great diagnostic chart on tuning "OVERSTEER vs. UNDERSTEER" at the "information" section on the ROGER KRAUSE TIRES web site.
http://rogerkrausracing.com/pages/moreinfo.html
Gives handling characteristics vs. corrective actions for a myriad of conditions...tires sizes, rubber compounds, shock settings, roll bars...lots to think about...more than I can deal with...
I stop at fiddling with tire pressures..actually, you can get a LOT of response with only tire pressures...the rest takes more expertise than I have or track time than I can afford.
Pete