Don't give away too much information about yourself
Restricting what others can find out about you online:
- Reduces the risk of identity theft
- Reduces the risk of property theft
- Prevents other people finding out things about your social life that you'd rather keep discreet
On social networks e.g. Facebook:
Use the privacy settings to restrict how much data others can see, especially people who aren't already your friends in the physical world (e.g. see http://www.facebook.com/safety/).
Tell people only the bare essentials in your out-of-office emails. Use a vague statement like "I will be unable to respond to emails until the 20th" rather than "Off on holiday till the 20th" (which implies the house is empty!)