As the Facebook of the corporate world, LinkedIn has been providing professional referrals for its users—which today number 645 million—since its debut in 2003. If you have only a vague memory of creating a profile, we've collected some facts and tips on how to get the most out of the internet's most valuable electronic business card.

1. LinkedIn can penalize people for being too ambitious.

LinkedIn wants you to reach out and establish connections with professionals who might be able to further your career, but the company would prefer you not turn into a pest: user accounts can be restricted or deleted for sending out too many invitations when the recipients indicate they don’t know you.

2. LinkedIn can hurt your job search if you're not careful.

Sometimes artificial intelligence doesn't act very intelligent. When users update their LinkedIn profile to better articulate their current position or even change their status to “unemployed,” the site likes to deploy a mass email urging your contacts to “congratulate” you on your new position—even if it’s the same position, or no position at all. If you’re in the job market and potential employers think you’ve landed something, you might be out of luck.  (You may want to turn off a feature labeled “activity broadcasts” so contacts aren’t alerted every time you sneeze.)

3. LinkedIn endorsements may not matter. 

LinkedIn

Job hunters quizzed about how much stock they place in those little “Endorsement” boxes in a LinkedIn profile had a quick answer: they don’t really care. Because endorsements are so easily checked off, they don’t carry much weight. (And in the case of people who barely know you, might not even be accurate.) Instead, try to aim for “Recommendations,” the personalized mini-letters of endorsement that colleagues can post to your profile.

4. LinkedIn loves to see shiny new profiles. 

Your electronic resume might be so perfectly worded and arranged you’re reluctant to mess with it. You should: LinkedIn’s search interface places value on profiles that feature a revolving door of fresh content, even if it’s just a single update about a new project or a new buzzword for work you’ve already been doing for years. Doing so can help a profile stand out in contrast to a laundry list of aged-out accomplishments.

5. You probably don't know you're being watched on LinkedIn. 

LinkedIn takes a sizable chunk of its profits from Recruiter, the site portal available to head hunters looking to fill jobs. By paying for the premium service, recruiters are able to surf profiles anonymously, stick a dossier to your profile with their own personal notes, and generally peer in on you while you’re none the wiser. One recruiter told WIRED that someone who lacked a LinkedIn profile entirely had zero chance of getting hired, even if he came across them through another channel. A lack of one would be a “red flag.”

6. LinkedIn finally realized they sent out too many emails.

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To be a LinkedIn member is to choke on emails updating you on your contacts' updated profiles, your new job opportunities, and several additional reminders about each. In 2015, LinkedIn acknowledged their ticker-tape parade of messages was too much for most people and announced they would be reducing their one-sided correspondence by 40 percent.

7. There are a few words to avoid on LinkedIn. 

Are you motivated? Creative? Passionate? Congratulations—so is virtually everyone else looking for work. Catherine Fisher, senior director of corporate communications for LinkedIn, told Fast Company that those were three of the most overused and ineffectual adjectives in profiles. She advised users to show motivation—not just tell—by offering specifics on projects or jobs they’re passionate about.

8. LinkedIn had to settle a class-action lawsuit. 

In 2013, many LinkedIn members were perturbed to discover that the site had used their imported email contact list to send out invitations to join the site by using the original user’s name. According to Business Insider, a California district court found that the site had not overstepped its Terms of Service policy with the initial introductory email—but it did take advantage by sending two follow-up emails. LinkedIn denied wrongdoing but agreed to a $13 million settlement.

9. LinkedIn isn't Facebook, but photos still matter. 

LinkedIn

Research has been done into how long job recruiters stare at profile photos, and they apparently like to peer into your soul for quite some time. Photos with “creative” filters, group shots, or clutter aren’t likely to endear you to viewers. Opt for a headshot that skips Photoshop and lets your personality come through without being too eccentric.