Employers are increasingly paying attention to what their employees and prospective employees are doing on social media sites. This can be a good thing or a bad thing, depending on what you're doing online.

Ways Social Media Can Help Your Career

Using social media sites wisely can help your career in a number of ways:

• Building your knowledge base. No matter what field you're in, there almost surely are dozens of blogs and websites where people with an interest in your field gather to share information and ideas. If you regularly participate in these networks, you'll be constantly learning and becoming aware of new business trends and even have the ability to connect with well-known experts in your industry!
• Building your credibility. By blogging about your field, contributing or commenting on other people's blogs, and participating in industry conversations on Twitter, LinkedIn, and other networks, you'll begin to build credibility as someone who, at a minimum, has an immense amount of interest and passion for the field. Put yourself in the shoes of an employer—who would you rather hire, a candidate with a demonstrated track record of interest and ideas in your subject matter, or someone for whom may not be as engaged or passionate?
• Establishing yourself as an expert. If you participate enough in the activities above, and you do it well, over time you can even start to build a reputation as an expert in your field. While this doesn't happen overnight, putting forth the effort and resources (with time as the largest of them all), you have the ability to create a reputation as a thought-leader in your respective field.
• Dramatically expanding your network. This kind of online participation means that you'll start to build dozens of professional contacts—people who you can call on when you're job searching or seeking professional advice. Keep in mind, of course, that an expanded network is a two-way street. Your network should in turn be able to come to your for advice or assistance as well.  

Ways Social Media Can Hurt Your Career

As much of a boon to your career as social media can be, it can do harm if you don't use it thoughtfully. More and more employers are googling job candidates and current employees, and sometimes what they're finding is really damaging.

It's understandable to think what you post online is part of your personal life and not something an employer should, or would, concern themselves with. However, on the internet there's no firewall between your personal and professional lives. It's all there for any employer who looks. So always ask yourself: Is this something you'd mind an employer seeing?

• The TV test, magnified. Maybe you've heard of the "TV test" for how professionals should conduct themselves. The test asks, "Would I be comfortable if this opinion, statement, action, behavior, or association were broadcast on national TV (sometimes without context)?" Social media is the evolution of the "TV test"—with potentially ever-lasting results.
• The internet is open for all to see. What you post on the Internet is not private, and it leaves a trail. Photos, status updates, tweets, blog posts, and comments on other people's blogs are all trackable—and can impact your reputation. The delete/edit button can lull you into a false sense of security, but the reality is that even things you think you've erased can be retrieved or live on inside search engines.
• If you wouldn't say it to your boss, don't say it online. I've seen job candidates whose online profiles included racial rants, inappropriate photos, political diatribes, and comments about being hungover or playing hooky. These are huge red flags for employers, and there's no shortage of potentially career-damaging gaffes, even some by sophisticated social media users
• "Privacy settings" aren't fool-proof. While privacy settings can give you the illusion of privacy, they're not infallible. Proceed at your own risk!
• That post may violate company policy. Many employers have social media policies governing what employees are permitted to post on social networks; make sure you know your company's policy!

I don't want to scare you off from using social media—quite the opposite. As described in the first section above, it can be a huge boost for your career. Just make sure you're being thoughtful about how you use it and understand the implications (both positive and negative) of how you participate in social networks.