What should you post? Metcalf says when looking for a job, try to focus your content and posts on the industry or area you're trying for.
"If you're focused on getting a job in, say, investment banking, then share information and comment on happenings in the industry. That way, when a recruiter does see your profile, you instantly have credibility as someone who is interested in and engaged with the industry and major players — you're branding yourself as a thought leader," he says.
Another mistake candidates make, Metcalf says, is appearing desperate in their interactions with hiring companies. Many will continually send and resend LinkedIn requests, or deluge companies' Facebook profile with comments or requests for interviews, and that becomes and instant turn-off, he says.
"Be respectful, first," he says. "You can certainly send a couple sentences about how and why you want to connect on LinkedIn, or comment a few times on Facebook and express interest, but beyond that you look desperate, and you'll never get a job," he says.
Mistake 4: Unbalanced Online Content
If your social networking connections are a mix of the personal and professional, you need to make sure you're not perceived as "partying" more than working, says CEO and co-founder of Strikingly.com David Chen.
Chen's company offers a one-click solution for users to create personal websites that can serve as online resumes or portfolios, and offers integration with LinkedIn to better showcase job-seekers' talents, he says.
"You're not only being judged by the personal content versus professional content you post, it's also about the ratio of non-work-related posts that show up in your feed," he says. If too many "personal" posts are appearing, you may come across as someone who's not dedicated or serious about your job or professional responsibilities, Chen says.
"A good rule to follow is this: one third 'interesting content' posts, one third 'informative' posts and one third 'promotional' posts," he says.
Mistake 5: Ill-timed Online Content
Another common mistake, Chen says, is the timing of your social media activity. Because most online content is time-stamped, your current or future employer can easily determine if you're regularly posting online content during work hours, and depending on their policies, that can get you fired, he says.
"Are you blogging or Facebooking during work hours when you shouldn't be? Your boss or a vindictive, catty co-worker can easily catch on, landing you a warning or a meeting with the HR department," Chen says.
Care.com's Duchesne advises taking your cues from senior leadership in your company to determine when, how much and what type of content is appropriate to post.
Mistake 6: Making a Poor Online First Impression
Sign up for CIO Asia eNewsletters.