you are going to find his hard....i would start with online press release sites, they are doing tremendously well at the moment and giving lots of clients (including mine) great results. Depends on your niche and if you have an important message that will catch on and get massive media attention.
I dont think you should write it yourself you better off hiring someone that does it for a living or even a close friend who is good at doing
PR stuff.
you should stick with prweb.com and prleap.com
but PRweb.com is the best - go with the $80 the one that has backlinks to google and other major news sources.
seriously I I sent an release through prweb.com and tryed others but prweb gave me triple the results that the others gave.
cheers
hope this helps.