Unlike the real world, where doing press releases is a slow, laborious process, in the on-line world, sending a single press release can result in extremely wide distribution and almost immediate feedback. The first key is to use a press release distribution service such as PRWeb. PRWeb already has a huge network of writers, editors, webmasters, bloggers, etc. who voluntarily receive press releases. You can also have the press release injected directly into search engine news results.
One powerful aspect of online press releases is how fast your information is distributed. Upon sending a press release, your information could appear on news-oriented web sites in 48 hours or less. These sites will now link back to your site. Also, if you use keywords in your press release, you could quickly achieve high search engine rankings for those keywords. In a 48 hour period you could create hundreds of new, keyword-loaded links pointing back to your site.
You need to take great care when composing your press release. You need to think in terms of both compelling, interesting copy, and of search engine optimization. Use your keywords as near to the top of your copy as possible, and use them as often as possible without sounding spammy. If your press release contains a strong call to action, that is even better. You want to compell readers of the press release to visit your web site for more information.