Better safe than sorry...
Do not give away phone numbers and email addresses unless necessary. There are many who sell data for money.
Experts caution against uploading personal photos on social media too frequently.
Many social networking sites offer good privacy settings. In Facebook, for example, you can limit access to your timeline to friends only, and the public will see only your profile.
Beware of public Wi-Fi (the ones at home are encrypted).
Close down accounts in online services, especially social media sites, that you no longer use.