Press releases and media advisories are two ways in which advocates can alert relevant members of the media to their core issue, public events, or significant happenings around their work. Media advisories are typically used to try and build attendance at a public announcement or event; press releases are typically used to announce newsworthy developments, such as the filing of a lawsuit, the formation of a formal group or a partnership with another group, etc.
Develop a standard format for press releases for your group that clearly identifies who you are; why your organization exists (possibly including a concise version of your mission statement); includes any logo or brand designs in the header; and provides appropriate contact information for interested journalists.