What are the biggest mistakes people make in press releases?

Over-selling and hype
Journalists tune out superlatives. "Innovative," "revolutionary," "industry-leading"—these words have no meaning and signal amateur writing. Let facts speak. If your announcement is significant, journalists will see it without marketing language.
Burying the news
Starting with company history, mission statements, or background kills your release. Journalists want news, not biography. Get to the announcement in the first paragraph.
No clear why
Explain why this announcement matters *now*. Why should anyone care? Who does it affect? A release that lists facts without context leaves journalists guessing. Make the relevance explicit.
Jargon and insider language
Write for readers outside your industry. If you need acronyms, spell them out once. Avoid technical terms without explanation. Journalists may not know your field; don't assume they do.
Too many cooks
Press releases written by committee often become bloated and unclear. One person should draft it. Let others review, but avoid adding layers of corporate language in revision.
No legitimate news
The biggest mistake isn't the writing—it's sending a release when nothing newsworthy actually happened. If you can't justify why this matters, don't send it.