The number one rule parents should watch out for is not to download stuff you don't know. You could be downloading a RAT or getting your device bricked.
DO NOT give your password to your friends in any situation because they might go on your social networks and make a bad impression about you. This can cause you to have depression just because you told somebody your password and they posted something bad about you on your social network
Do not text and drive. You could get in a car crash if you look down at your phone while driving. This could cause serious injury or could cause you big trouble.
If you have a Webcam at home make sure you put tape over it so that if somebody hacked your webcam, they can't see you doing something private.
Never put to much personal information on your social networks or else will blackmail using the information/pictures that is on there.
Beware of the pictures you are posting on your social networks, if you try to delete them, they will still be there even if you can't see it.
If you got a text message from somebody you don't know, don't answer because somebody might be trying to get in a relationship with you that you might not like.