Caster or camber or both?

Camber is best set so the tires' contact patch is as big as possible at all times. So with a stiff suspension you'll need less camber than with a soft one.
If the tires wear evenly across their contact patches, camber is about right.
On really bumpy tracks, adding a little more negative camber (2 to 3 degrees) can help traction and reduce the chances of catching a rut and flipping over.

More More caster aids stability, and handling in bumpy sections.
Less Less caster increases steering drastically.
Steering feels much more direct, the car turns tighter and faster.

Here is a very good site on handling.
http://home.scarlet.be/~be067749/58/