Business owners today are lucky to live in the golden age of self-promotion. Thanks to Twitter and Facebook and a dozen other social media tools, publicizing a company has never been easier or more affordable. As long as you have a computer and a decent grasp of language, you can probably do a pretty good impersonation of a public relations professional.

But public relations – the real stuff – is about more than likes and retweets. And nearly every serious small-business owner will eventually come to realize that to really grow a business, you need the help of a professional.

“All businesses need to publicize and market what they’re doing,” says Eric Tyson, author of Small Business for Dummies. “The question is when does it make sense and when can you afford to hire somebody to do it.”

First, some things you can do yourself: Establish a social media presence and keep it lively (solicit feedback, run contests, send exclusive coupons to followers). You can also probably pitch local media on your own. “A lot of town papers are always looking for editorial content they don’t have to pay for,” says Tyson. Consider writing a column that relates to your business without overtly trying to sell anything. “As long as you don’t send them something super promotional, they’ll be wiling to run it.”

But for the bigger stuff (national media, press conferences, large-scale promotions), you should partner with a professional. And that’s going to cost you. A large PR agency can easily charge business clients $20,000 a month. On the other hand, it’s not hard to find a good freelancer who’ll work for $50 an hour. This is just one reason it’s important to shop around.

Case Study of a Good PR Hire

That’s what Julie Bashkin did when it was time to hire PR help for The Klutch Club, the online health and wellness company she founded in April 2012.

“First I scoured my entire network for anyone I knew in PR,” as well as for media people who regularly worked with PR people, she says. She organized the candidates by size of their organization (she wasn’t sure what size agency she wanted, so she interviewed a range), examined their client lists for relevant experience and asked for further references. She ended up interviewing 10 candidates.

Bashkin had very little experience with PR, but her priorities were clear. “I wanted someone who would be high level and strategic with a lot of experience,” she says, “but who also had time for me.”

She wanted someone with a passion for her work. The Klutch Club proposition is a little tough to explain – for a small monthly fee, customers receive a variety of healthy products to sample each month (like a beer of the month club for people trying to live healthier lives). Bashkin was careful to look for PR people who had worked for health and wellness clients and gotten them results.

In the end, the right choice turned out to be Samantha Slaven Publicity, a boutique shop in Los Angeles. Bashkin put the agency on a six-month retainer, and was very happy with the results. Slaven got the business placed in Self, Shape, Glamour, Cosmo and more.

In December, the Klutch Club moved its rapidly growing account to a larger agency in Chicago where her business is located. But because Bashkin was careful to choose someone who had experience with her industry the first time around, the relationship continues to pay off. Slaven is “really good about integrating us into other opportunities she finds that are mutually beneficial for us and her clients,” says Bashkin.

How You Can Hire Smart Too

Questions to ask when interviewing a PR firm: It’s a PR agency’s job to sell your company to the media, so it’s vital they understand it. Ask them what their media strategy would be for your brand, then ask to talk to similar clients for whom they’ve gotten results. Be specific. “Any agency can produce one or two satisfied clients,” says Tyson. “Make a specific request for a company similar to yours.” Also ask who will work on your account. PR firms may send senior staffers to the pitch meetings, then handle your account with junior executives (or worse, interns).

Negotiating the fee: While some PR firms these days are experimenting with a pay-for-results structure, either by taking equity in the company or building incentives into their contract, most still bill by the hour. If you’d prefer to pay based on results, feel free to suggest that to your potential firm. It will not be the first time they’ve heard it. Just don’t be surprised if they say no.

Results, sooner or later? If you’re promoting an event, you should expect results pretty quickly. Otherwise, be patient. PR is about relationships, and it can take time for lunches and phone calls to translate into actual media hits. Also bear in mind that some magazines work on lead times of several months, so good work today might not pay off till the weather turns. That said, if three to six months go by without any tangible results, it might be time to re-evaluate.