Anyone can write a press release, getting it distributed is the real key. There are a number of sites that are experts at this, such as PR Web. Such sites have a significant distribution list and are the fastest way to get your message out there. It’s also a good idea to embed some links to your site in the press release as this will help drive additional traffic to your site as well as allowing for some SEO advantages.
For example, my friend runs the site Life Insurance Calculator. After creating some press releases around industry statistics, my friend found that many other sites posted his press release online complete with links back to his site. A form of free advertising!
The issue is that for your press releases to be picked up the content has to be reasonably unique. This is especially the case if it is to be picked up in main stream media. In order to achieve this, ideally you need to collect some data that is unique or have a unique point of view on an interesting topic. Using the example of my friends site again, via his website he collects data on the average policy size for trauma insurance. This is particularly useful information put in a press release, as it is not widely known what this statistic is. Presenting new information often gets picked up in mainstream press releases.
To use another example, the site Forex Platforms specialises in providing FX Strategy. The experts produce videos on their FX predictions. In addition to the video analysis, this site is crying out for regular press releases on what the experts are tipping. This could get picked up by mainstream media as it is quality unique content.