Chris wrote:generate warm feelings towards a particular being initially
The sequence I follow is, towards me, then my son *, my wife, my parents and brother, my whole family and friends, then some co-workers and neighbors to whom I have mostly neutral feelings, and then to those people a hold some kind of aversion, then people I do not know but who committed horrible crimes, the beings in the hell realm, the beings in the celestial realm, everywhere.
* at this point usually I remember the Karaniya Metta Sutta passage:
As a mother would risk her life
to protect her child, her only child,
even so should one cultivate a limitless heart
with regard to all beings.