You've heard the warnings.

Don't upload photos of yourself drinking directly from tequila bottles. Don't blog about your mind-numbing job. Don't post volatile rants -- unless you're looking to offend your boss, upset your mom, maybe even lose a beauty-queen title.

For the average employee using a social-networking site, though, wild party photos and shocking language probably aren't the issue. It's the subtler things: the stuff you'd never want to share with your boss, but -- through Facebook or MySpace -- unwittingly do.

Think embarrassing comments from a maturity-challenged former roommate, goofy pictures from last summer's vacation, or the time stamp showing you were playing Scrabulous instead of meeting an important deadline.

Online social networking, originally the playground of a pre-workforce demographic, is now commonplace in offices. How do we navigate this new landscape, which builds business contacts and feeds friendships even as it creates a collision between the personal and the professional?

Ignoring these sites isn't an option. MySpace, LinkedIn, Friendster, Facebook, even niche sites like Digital Rodeo -- the list continues to grow. More than half of Facebook's users are now outside college and the company says people 25 and older are the fastest-growing group on its site.

Opting out could brand you as unenlightened, and signing up but refusing "friend'' requests from co-workers or your boss is an uncomfortable solution. Rejection's ill will could even trump the fallout from embarrassing photos.

Like company picnics or after-work drinks, the trick is balancing what happens tonight with what you face in the morning.

"Exercise caution,'' says Sue Murphy, an executive vice-president at the National Human Resources Association in the United States. "Once you allow someone in, they can link up with the other individuals you have listed as friends.''

At many social-networking sites, any "friend'' can post comments or upload photos to your page. On Facebook, a rotating selection of a half-dozen people from your "friends'' list appears on your page each day, with their chosen profile photo attached. There's no way for your boss to know whether the "friend'' using an image of Spongebob Squarepants or Marilyn Manson to identify himself is your closest confidante or a relative stranger.

Sound perilous? Fortunately, there are ways to minimize the risk to your professional image:

Keep your public pages as career-focused as possible.

Occasional banter is fine. But think before you post: "Would you put this up in your cube or in a common area where you work? If not, don't put it on Facebook, because that's what it is _ a virtual analog of your office,'' says Curtis Soldano, a videogame producer from Redwood City, Calif., who has used several social-networking sites.

Murphy suggests two separate pages, one professional and one personal. As acquaintances ask to link with you, direct them to the proper page. For extra security, choose a personal page that can be password-protected, such as a Typepad blog. Don't have time to manage several pages? Consider using drop.io, a free site for privately sharing files or messages, when you want to share anything sensitive.

Choose your "friends'' wisely, and ask that they treat your page with care.

Your posts may be pristine but that doesn't keep friends from adding embarrassing comments or linking you to provocative content. Facebook is usually set to alert everyone on your "friends'' list when someone writes on the public "wall'' of your page.

After posting a photo of himself dancing on Facebook, Roy Chacko had a friend post a comment about it, "and she used an offensive word. I know she doesn't mean it the way it sounds, but other people don't know her,'' says Chacko, an assistant manager in on-air promotions at HBO in New York. "If people I work with see that, I don't want them to get the wrong idea.'' Chacko quickly removed the post.

Try warning friends that your page is seen by your boss and/or co-workers, and ask them to skip edgier posts. Also, exercise care in linking with people you barely know and can't predict. "Part of the glamour of it is how many friends you have,'' says Gary Wipperman, who oversees computer systems at Wartburg College in Waverly, Iowa. "But think about it: These are people you don't know. Are you gonna invite them into your house?''

Choose wisely about how much time to spend signed on.

Using Facebook's "stay logged in'' feature can be fun and convenient. But co-workers who see you perpetually signed on may assume you're killing time searching for friends and chatting. Posts are time-stamped, so it's easy for people to calculate your time online.

Does your company have a policy about using social sites at work? Many offices have tackled this issue regarding instant-messaging sites. If there's no written policy, consider discussing it with your boss.

Think about the details.

Adding "status updates'' to your page can be fun. But even if the posts aren't controversial, think about how they'll be received. If you're on vacation and everyone else on your team is working, typing the words "I'm sipping a margarita on the beach!'' may not be wise. "It's not even necessarily that they don't know you're on vacation,'' says Sam Lessin, co-CEO of drop.io and a steady Facebook user since it launched at Harvard University. "But do you really want to put that in the middle of their faces?''

And add extras to your page with caution: "Certain applications carry with them certain implications,'' says Soldano. "If you decide to add the 'Am I hot or not?' widget,'' that sends a certain message.

Stay on top of your accounts.

There's no need to check your pages hourly, says Wipperman, but casual users who rarely check are more vulnerable. Chacko has had friends reply to private Facebook messages by writing on his public "wall.'' Even if the content is benign, he says, "everyone doesn't need to see this.''

Still, even a brief appearance of something embarrassing can have long-term impact. On many sites, it's not possible to know who has visited your page, so you can't do targeted damage control after an embarrassing post. And "some browsers cache pages, so you're never sure which version will pop up'' in the future, Murphy says. She advises employees to keep the tightest rein possible on their pages.

Particularly if you're going to be looking for another job.