People just like the good workers they already have. And one of the best places to find them is among the friends and family of those valued workers.

Explains Jaime Churchill, a member of the Disciplines Special Expertise Panel of the Society for Human Resource Management: "Because people tend to associate with others who are similar to ourselves, our friends and family are likely to be able to successfully assimilate into corporate culture as we did."

That’s why 70 percent of companies surveyed by Meritage Talent Solutions in 2014 reported having some type of employee referral program.

Now, since many people connect with friends and relatives on Facebook and other social media, that’s where a growing number of employers are prompting workers to tout available positions.

Firms can use special software that "encourages employees to post on their social networks and make referrals by making it easy," says Daniel Kieve, spokesperson for Zao, one of the software providers.

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For instance, with Zao software, workers can elect to activate autopost, allowing open positions to be posted on the social networks they select, and with the frequency they want.

Another firm, Zalp, offers software that lets employees link their social media accounts to the employer’s system and select how frequently as well as what type of open jobs – like those in a specific geographic area – they want to post.

For the jobseekers, it’s worthwhile to keep up with friends via social media, says Christine Walters, author of "From Hello to Goodbye: Proactive Tips for Maintaining Positive Employee Relations" (Society For Human Resource Management, 2011).

Walters says studies show that referred candidates tend to call for interviews more frequently and also get hired at a greater rate than applicants without a referral from a current employee.