are you talking about mainstream or adult? in adult, you submit to xbiz through their prblaster (xbiz.com/services/prblaster), you have to email
[email protected] with your release to them, submit to adultchamber, and you used to be able to do it through klixx as well, but i think they went defunct.
as far as how to write a press release, use the below resources along with looking at other written releases out there to get the best one for you
wikihow.com/Write-a-Press-Release
en.wikipedia.org/wiki/News_release
we got most of our traffic back from xbiz, then avn came next
but in non-adult its another world and process, let me know if thats what your talking about
good luck