Social media has set up camp in the professional world and is there to stay.

Social media sites are no longer just places to reconnect with childhood friends or college roommates. Companies now use social media websites to do unofficial background checks on potential employees.

A Cross-Tab Marketing Service study, released earlier this year, reveals that 70 percent of companies have rejected a candidate based on an inappropriate social media website posting.

This is a scary reality for everyone who uses these sites as a harmless way to catch up with friends, but may have crossed the line by uploading funny, yet work-inappropriate pictures. In today’s world, a world inextricably tied to the Internet, anything posted on a public page can and will be found by potential employers, says Lew Clark, an attorney with Squire, Sanders and Dempsey.

However, there are ways to prevent shooting yourself in the social media foot and, if you’re smart, work the system.

There are a few obvious things not to have on Facebook, MySpace, Twitter, YouTube or other social media websites — including inappropriate photos or conversations. Poor grammar, spelling or writing skills, use of profanity, and poor people skills also can turn off a potential employer, Clark says.

“One of the huge no-nos that we discuss with folks … is to never, ever post anything negative about a former boss, co-worker, employer. It creates the wrong image. No matter if it’s true, valid, anything else, you just do not want to go there,” says Cindy Jones, vice president of human resources at Synergy Seven.

Don’t despair. Companies aren’t just looking for reasons to disqualify you. They’re also looking for reasons why you’re perfect for the job, Jones says. Especially on professional social media sites, such as Linkedin, companies look to see prospective employees’ connections.

If used properly, social media can be an effective marketing tool, Jones adds, providing a real-world example of how to use social media as an advantage.

When a woman decided to switch careers from Realtor to sommelier, she changed both her professional — Linkedin — and personal — Facebook — social media pages to reflect her new career path. She posted her excitement about passing tests toward receiving sommelier certification and changed her main picture to one of her toasting with a glass of wine.

While this type of online makeover won’t work for all fields, Jones says it’s an example of using social media to one’s advantage.

“There’s nothing at all improper with a prospective employer (looking) on someone’s public Facebook page, their public Twitter page, or any other online networking website that you can access publicly,” Clark says.

However, accessing a potential employee’s private page by figuring out the password, accessing it through someone else’s page or by pretending to be someone else is illegal, he adds.

Aside from accessing a page illegally, employers can find themselves in other sticky situations.

Employers may find information about a person’s religion, health, age or personal life that they wouldn’t otherwise learn and can’t legally take into consideration in the hiring process, Clark and Jones say.

“The risk to the employer is that someone could allege that you used information that is legally protected to decide whether to hire somebody or not,” Jones says. “Our guidance with most companies starts at the place of there’s nothing illegal about it, but be careful.”

Clark adds: “Employers are looking for whatever resource they can to try to get information about candidates so they can make a good hire.”

Background checks, including checking social media websites, can reduce costs, encourage honesty among employees and ensure the best person gets the job, says Marcia Rhodes from WorldatWork, a global human resource association.

Although using social media in the hiring process offers many perks, Jones and Rhodes say they’ve seen a trend in which companies are limiting social media background checks on possible employees, contrary to the report previously cited.

Kim Magyar, an attorney with Snell and Wilmer, says she doesn’t see the number of companies using social media decreasing, but companies are being more targeted and cautious with their searches.

Some companies wait until they’ve already interviewed a candidate to check social media, while others check before they conduct an interview, says Magyar, who has given presentations on social networking and the workplace.

Many companies believe social media can be a treasure trove of information; information that might not always be accurate, Magyar says.

“There’s nothing to prevent an employer from making decisions based upon what they see (on social media sites),” Clark says.

Nothing, except the awareness that public social media pages are fair game and the preparedness of prospective employees to maintain their pages in a way that represents them in a respectable, hire-able way.