First thing to remember is not to use the same password for every social networking account (Twitter, LinkedIn, Facebook, etc). Social networks users often have a false sense of security: they are mostly communicating with people they know (family and friends), so they tend to think nothing bad can come from their friends' accounts. But friends can be tricked into using malicious applications that post malevolent links or send spam e-mails with links to phishing pages. Social network accounts do get hacked (mostly because of weak passwords, password-stealing e-mail scams, stealing credentials via unsecured connections, etc) and cyber-crooks may post malicious content or use gathered information for identity thefts.
Links to tutorials that help securing your Facebook, LinkedIn and Twitter profiles are in the end of this article.
Think before you click a link
Stay cautious about strange posts and especially links. Posts like "OMG! You got to see this" or "Is that you on the video??" are examples of common scams.
Very typical behavior of a malicious app or post is to ask filling a survey before showing you the promised video or post. While the survey itself is not usually malevolent (but still earning dollars to cyber-crooks), it is followed by asking for your personal information such as full name, phone number, credit card number, etc. This is the place to really stop and think - why would displaying a simple video or news story need this? That's where an alarm should ring in your mind. Close the survey window right away and notify your friends about malicious app you just found. If you installed an app, remove it.
Verify that links lead to the promised web site, not a phishing page
Watch out for phishing pages - always double-check links that open a login page, no matter how authentic the page looks. Take a look at browser's Address Bar and see if you really are on the real web site or a page that tries to steal your user name and password.
Use HTTPS, not HTTP
Always log in using secure protocol (https) - this keeps your user name and password safe. If possible, turn on safe browsing option in configuration page.
Friend or foe - do not accept friend requests from unkown persons
To harvest information and gather compromising photos or videos, fake profiles have been set up by cybercrooks in every social network. There are both automated (bot) profiles and phishing profiles (operated by humans) and they have very tempting (read: hot) profile pictures.
First, don't go opening a profile just because it has an attractive photo. How big is the chance that an unknown and really hot young person wants to be friends with you - just like that, out of the blue? It really does not happen this way. Forget it and deny the request.
Second, spot the strange facts (because you're already visiting the profile ): mostly empty Walls and Timelines where each post has about gazillion likes; photo albums that have only a few photos, each of different person; biographies that just do not seem real (clearly underage person working as a director of some huge multinational corporation), etc.
Think before you post - can the information be used against you later?
Do not post sensitive information: your passwords, secret work projects, semi-nude or nude photos, etc. For example, "I think I drank too much at the party last night" might get you in trouble if your fiancé knows that you were home sleeping that night. And don't call names on other persons, the information might harm you a lot in the future!
Limit visibility of your posts
There is no need to share your status updates, photos, videos and other stuff with the whole world. If possible, create different groups of friends and make your data visible to appropriate people.