Mike Manuel links to Valleywag’s amusing post on how to leak. It does offer good insight into this noxious process.
Unless you have evidence of serious wrong doing or a threat to public safety, speak on the record.
Too often leaking is just about showing off. It is degrading to our public discourse when no one will take responsibility for their words. This evil practice is reducing citizens and reporters to informers and secret police. Living in freedom means speaking openly. Maybe you have to live in greater Washington, DC and see the damage up close to comprehend its corrosive effect.