Be cautious of links and downloads.
Do not download or install software or anything on your computer or cell phone before checking with your parents or guardian.
Be considerate of others when posting pictures.
Do not post inappropriate pictures of anyone.
Build your own brand.
Your online presence is your personal brand so make it is positive! Protect your reputation. Only do things online that would not be embarrassed for anyone to see - your parents, your grandparents, your friends, your future boss, etc.