I don't know what posts you are referring to (I can't see any about adding a familiar in d20 going back 4 years, were you thinking about Pathfinder?) - except for either making a
Class Variant in the editor that allows a Familiar, or by having your Hero take the "Obtain Familiar" Feat from Complete Arcane. There is no adjustment in d20.
If I'm wrong, maybe Sendric can correct me. (Or anyone else!)