Hi R
The following reading set me on the right track when i did the same a couple of weeks ago:
SiteProNews: The 10 Commandments of Press Releases
SiteProNews: Powerful Press Release Distribution Tips
SiteProNews: Success Strategies for Optimizing Online Press Release Campaigns
The last one was my gospel.
Although another handy hint: Don't just distribute your press release online. If you have a niche, contact the publications for that niche or even local papers.
I did this and unknown to me until a friend told me, I got into the local paper word for word which is a rarity.
HTH