  We provide a systematic treatment of self-averaging identities for various
spin systems. The method is quite general, basically not relying on the nature
of the model, and as a special case recovers the Ghirlanda-Guerra and
Aizenman-Contucci identities, which are therefore proven, together with their
extension, to be valid in a vaste class of spin models. We use the dilute spin
glass as a guiding example.
