When using the Internet, remember the following things:

• Never share your passwords with other people, not even your best friend.
• Never reveal your surname, address, place of residence, e-mail address, phone number or the name of your school with strangers. 
• Do not give pictures or private information about yourself or other people to strangers on the Internet.
• Ask your parents for permission when signing up on different websites and gaming services.
• Remember that no one can make you do anything online! If you do not feel comfortable, you can always leave.
• Tell your parents or other adults if someone keeps sending you inappropriate messages or images online. 
• Remember that the people who you meet online may not always be who they say they are. 
• Never meet an online acquaintance in real life alone! 
• Do not answer inappropriate or insulting messages from strangers.
• Do not send inappropriate or insulting messages to others. Be respectful and take others into consideration.

Source: http://www.edu.fi