Oh yes, I was going to list a few of the rules - well, mine anyway.
1) Date it
2) Check you've dated it.
3) Make sure you've answered the big five - who, why, what, where, when.
4) Give contact details for further info
5) Make sure the contact person is available (don't write a release and then go on your hols!)
6) Make any embargo clear.
7) Go back and check again that you've dated it.
1) Write the whole story in the first line or paragraph
2) Try to avoid writing anything longer than a page
3) Quote somebody saying something that adds to the story. Not bland PR puffery.
4) offer images (or AV) if you can.
Sure there are others but can't think of them right now.