Finnegan summarizes it very well.
For a primary street car that sees a few track days a year, simply remove your guide support pins and max out the camber. You can get about -1.4 deg front if not lowered.
For a primary track car with some street duty, you can go in the low-mid -2's.
For a race car probably around -3.
My rear camber has always been very similar to my fronts, perhaps slightly more positive.
For the E9x M3 it seems that it does not need as much static camber as the E46's... probably due to a more aggressive dynamic camber curve.
E92 M3 DCT