First, what is a press release? It’s a news item, written in complete sentences, with standard punctuation, in the classic inverted pyramid style that you should have learned in the fifth grade. That means that if an editor were to chop your press release off at the end of any paragraph, the result would still make sense and appear to be a complete news item.
Next, what isn’t a press release? A file description is not a press release. In your descriptions, you have very limited space, and must cover all the basics, so shorthand expressions and sentence fragments are OK. Things like: “Includes config. help.” or “Fully configurable.” work in a file description. In a press release, you have to use only complete sentences. Bullet lists don’t qualify as sentences – rewrite your lists as paragraphs.
Not an instruction manual: It’s tempting to cut and paste press releases from your instruction manual, isn’t it? Don’t do it. The result may be clearly written, but it’s not a news item. At best, it’s a features and benefits list. At worst, it’s a general introduction on how to use your software. Save that for the help file.
Not an advertisement and not a review: If you describe your program as “the wonderful new utility” with “a plethora of new features” the editor will either throw out your puffed-up verbiage, or your entire press release. The latter is more likely. If you include anything in your release that reads like a review, an editor will have to decide if the text reads like a product endorsement. Endorsements will get pulled out and printed (by you) with their byline, stating how wonderful they think your product is, so they won’t make it into a news item.
Finally, don’t get fancy. A magazine can’t take your press release and paste it into their New Products section if you included anything that their organization style sheet doesn’t allow, or that would turn into garbage when pasted in. You don’t have the style sheet for each publication, so you need to write conservatively if you’re to gather any ink at all. If you’re using any of these things, cut them out: Latin expressions, such as ad infinitum, etc., unusual punctuation, such as bullets, ellipsis, or circumflexes, quotes from yourself describing the fun you had creating this new product, and everything else that isn’t actual news.