However, that's not always possible. If you're scrambling and haven't had time to do that, you can always reach out blind or use services/agencies to help. There's a YC company called PRX that helps with this and does it at a very affordable price. Another cool site that was on Product Hunt recently ranked a bunch of media outlets - http://presshour.co/?ref=producthunt. Lastly, take a look at your competition and who covered them - those are probably your best targets.