Requirements

Quote from Book of Exalted Deeds:

Only intelligent characters of good alignment and the highest moral

standards can acquire exalted feats, and only as a gift from powerful agents of good—deities, celestials, or similar creatures. These feats are thus supernatural in nature (rather than being extraordinary abilities, as most feats are).

A character must have the DM’s permission to take an exalted feat. In many cases, a ritual must be performed; often this simply amounts to a character swearing a sacred vow, for example, in the presence of a celestial being. A character who willingly and willfully commits an evil act loses all benefits from all his exalted feats. She regains these benefits if she atones for her violations [...] A character with at least one exalted feat radiates an aura of good with a power equal to her character level (see the detect good spell), as if she were a paladin or a cleric of a good deity