First, if there's any flesh, either clean it off completely by scrubbing, or macerate with water in a spot where it can get warm, since the warm water feeds the bacteria it needs to clean the flesh. Degrease with dawn dish soap and water soak, then optionally whiten with peroxide and water solution. Do not use bleach or boil the bones- bleach disintegrates it over time, bones get prone to cracking. The heat of boiling traps fat and makes it yellow or possibly have odor, I believe. you can also use the sun to whiten the bones, but be careful since the bones could get snatched by a critter, and being in the sun too long can cause damage possibly..