Elizabeth Wasserman

The days when social networks were just for teens are long over: Adults now take up social networking for fun and business alike. One entrepreneur, Sheilah Etheridge of Anchorage, Alaska, uses social networks to turn up business leads for her home-based accounting and consulting firm. But Etheridge is selective with what she shares and where. “Everything we post on the Web is obviously out there for all the world to see, and it’s out there for eternity,” she says.

To get the most out of your favorite social networks, it’s important to be aware of how to protect your online privacy. Here’s how to share safely:

Tip No. 1: Don’t fork over too much personal info.

You don’t always know who is viewing even tidbits of your profiles, so think twice before you post sensitive -- or potentially embarrassing -- information, videos or photos on social networks. It could fall into the hands of identity thieves, prospective employers, college recruiters or even potential mates.

“People should assume the content they put online is going to be public,” says blogger  Jeremiah Owyang, a former senior analyst for Forrester Research.

Tip No. 2: Review privacy policies before you post.

Some networks, such as LinkedIn, have adopted privacy policies that vouch they’ll never share your information with other users without your consent. Other sites, like Facebook and Twitter, offer online privacy settings that allow you to control who can view certain information and who gets notification when you add friends or Web applications.

But be mindful about the details: On Facebook, for example, your profile and photo privacy settings are separate. Just because you block non-friends from seeing your profile doesn’t bar them from seeing your photos. Make sure your review all your preferences under Account > Privacy Settings.

Tip No. 3: Don’t reveal every step you take.

It’s a freaky thought, but stalkers, jealous spouses and suspicious employers can use social networks to keep an eye on your every move. Many photos and posts are time-stamped, so the date and time you post it is recorded and shared with your network of friends or connections. This means your boss may be able to find out how much time you spend on Facebook while at work.

Facebook also allows you to “Check In” where you are, revealing your geographic location. On Twitter, you can note your location in your tweets and in your profile. If you want to keep your moves and location on the down-low, avoid checking in altogether and tweak your online privacy settings.

Tip No. 4: Be smart with apps.

Most social networking sites are for-profit companies, and advertising keeps membership free. Any time you sign up for a free app or contest on a social network, your private data might be used to target you with online advertising based on your activities.

“The purpose behind social networking sites is supposed to be to enable you to connect with friends and colleagues and do these networking activities,” says John Verdi, senior counsel for the Electronic Privacy Information Center (EPIC) , a nonprofit privacy advocacy group in Washington, D.C. “What they don’t say is that ‘our real purpose is to mine your data and sell it to the highest bidder.’”

So even if you’ve read Facebook’s online privacy policy, you still need to read the privacy policies of application-makers who promote their apps on Facebook. “They are third-party applications,” says Verdi. “The social networks don’t vouch for any of them.”

Tip No. 5: Don’t expect to be able to delete it once you post it.

It’s happened to the best of us: being haunted by your old social network posts that never die. There is an assumption that you “own” your profiles. But that’s not the case.

In the past, Facebook users were not able to completely delete their profiles. Facebook claimed it wanted to store the information in case users wanted to revive their profile, but it has now caved in under pressure from users to allow for easier deleting. MySpace and LinkedIn allow users to delete their profiles too.

But when it comes to posts you leave on others’ profiles -- or content that friends copied off your profile or blog -- it can remain online for eternity. “There are going to be remnants or ghosts,” says Owyang. “Assume that everything you put online is forever.”

The single best thing you can do before you put yourself out there on a social network? “Speak to other users you know and trust before joining some sites,” says Etheridge. In other words, network a bit before you sign up for a network so you can learn more about how the site protects your info -- or doesn’t.