General suggestions to remember are to avoid really salesy, hypey or excessively promotional words and phrases like “revolutionary”, “One-of-a-kind”, “unique”, etc; always use the third person–never use the words “I” or “we” unless you are paraphrasing somebody else; keep it short and straightforward; and have a look at other good examples of PR releases to get additional steerage.
It might take some attempts to start getting the trick down pat but before you know it, if you follow these basic axioms, you will be writing effective press releases without even considering it.