If you don’t, it might be time to get acquainted. HARO stands for “If I Can Help A Reporter Out.” It was started by a PR guy and networking maven named Peter Shankman as a place reporters can turn to when they’re stuck for sources. Shankman started it as an alternative to ProfNet, which some writers have complained has grown so big the sources it nets aren’t relevant.

For reporters, HARO is easy. You don’t even need to register. Just go to the “Reporter” side of the service, fill out the request form and click “Submit it.” Your query will be included in an emailing of multiple requests for sources that Shankman sends out several times a day to a list of more than 23,000 PR representatives, company executives and other sources.

I’d heard a lot about HARO in recent months but didn’t give it a try until last week when I was hurting for sources for an IT industry story for IncTechnology.com that I was writing at the last minute. So I took the plunge and submitted a HARO request. Within 24 hours, I got about 40+ responses from PR reps, IT consultants and company presidents, etc. By the end of day two, I’d received close to 60.

HARO isn’t just for tech stories. I have freelance friends who write about all kinds of things, from green living to parenting to finance, and they all use it and rave about it. And they’ve been able to track down the hardest sources of all to get – real people.

HARO has grown so popular so quickly, it’s now got some of the same problems that plagued other source-finding services, namely too many off-topic responses, which you can read more about in this post about it on The Renegade Writer blog. Get around that by making sure your queries are as specific as possible. And state up front that people won’t hear from you unless you’re interested in using them.

If you decide to give it a try, I’ve got one more piece of advice: since HARO can result in inquiries from many more sources than you could possibly use, when you fill out the query registration form, give a very short time frame for people to get back to you, such as in 24 yours or less. Otherwise you could get bombarded.

And if you’re a PR person, read these great do’s and don’ts from Susan Johnston’s The Urban Muse blog about using HARO to pitch story ideas to writers.