jsmitty01..
depends on the type you're flying...aircraft and engine...( an inverted engine again requires different handling )..and even sometimes one engine may be a little more rich than another on aircraft of the same type...
also depends on tha altitude of the airfield...
but remember that fuel is cooling as well ...so the leaner the hotter and for close cowled high performance engines that could be a bad thing...
so by and large i would always use fully rich on the ground ( i am at sea level ) unless there is good reason to do otherwise.
dean