I used this tool

http://www.racerpartswholesale.com/product/1934/Caster_Camber_Gauges

and at the time, harbor freight sold (on their website only) a toe gauge.

I remember thinking, wow this is easy. And it drove very well. When I measured, I know I didn't get as much caster as people said I wanted. But it drives great at all speeds, so I didn't worry about it.