A good balance between luminance and saturation, as noted above.
I try to keep the green at about 50 IRE, and nice and even as you’d mentioned.
If you’re doing head-to-toe you’ll need to light for it, yes.
And noise is the enemy of a good key.
Beyond that, Chris’s comments on specifics are useful.
Also, shooting at a decent bitrate and 4.2.2 color sampling are useful. AVCHD can be…interesting in a greenscreen setting.