Some publications receive thousands of releases per week, making the sorting process for editorial staff extremely difficult. Begin main copy of the release prefaced by dateline, i.e. city, state, date. Head the page with a reference to the the topic of the release, followed by the page nnumber. A press release should be long enough to convey the news it is meant to carry. In most cases, one or two pages will suffice.
Reputable publications are unlikely to publish a story without some checking.
They may also want to get more information that will help them produce a story in their own editorial style, and this may include interviews and third party opinions. Less fastidious publications may run your release just as you mailed it. Paragraph length is also worth mentioning. Keep it short and to the point. Four to five lines should be about your limit.