http://www.ehow.com/how_8794_create-press-kit.html
Presentation is everything.
Don't cheap out. If the linen pocket folder looks the best, but costs a dollar more than the obviously cheaper version, go for it anyway. Remember, first impressions are important.
Include small promotional items, such as a personalized paper clip or a magnet, if you have them. These items often make it to the reporter's desk, and therefore, they keep your company name right in front of them.