Excess jargon will confuse your reader and may be enough for a journalist to pass over your release for one that is easier to understand. Leave the technical details for the phone call or follow up email. Once an editor contacts you, you might then give an interview or go into more depth on your particular topic. Chances are the editor will be more familiar with your industry, since he has taken the time to contact you.
Avoid flowery language, redundant expressions and unnecessary adjectives. These will detract from your story. And do not embellish or exaggerate your press release. If your release is written with embellishments, you will very quickly lose credibility. Keep in mind that this loss of credibility will carry over to future releases. Journalists will remember a source. They will remember a name. They will remember a web site. If you leave a bad taste in their mouth, they will remember the experience. This means the next time you submit a press release, which may be accurate the second time around, it will not be looked at because the journalist will remember you as someone who embellishes your press releases.