Details about your vacation - Although it's quite normal to get carried away with the excitement of going on vacation, it's a good idea not to share too much about it online like when you will be away and when you plan to return. This could be used by thieves to plan a break in to your house. Better plan? Upload this pictures, once you're back.
Privileged inside information- If you've signed a non disclosure agreement , this holds true while sharing online too. So be careful about casually posting such business related information online.
Complaints -Don't air you work grievances on social media online either . Someone might just see it. You don't want that happening do you?
Showing off a brand new buy- Not everyone is as lucky as you and posting such stuff will only cause resentment and hatred towards you. Plus knowing that you've got the cash will also attract people who are looking to take advantage of you.
Post copy paste status updates - You know those updates which state how Facebook is going to start charging from such and such a date if you don't re post this status etc. You know it isn't true. And sharing these only makes you look stupid and uneducated
