Prefer to place your PC in rooms such as the living room rather than in bedrooms. This way you will be able to supervise your child without him/her feeling controlled.
Make surfing the Internet a family activity. Use the PC with your children.
Tell your children about the dangers of chatting with strangers in chatrooms.
Talk to your children about safety issues (communicating with dangerous people, accessing sites with harmful content) that arise from surfing the internet.
Teach them not to give out personal information without your permission (last name, first name, age, home address, phone number, family income, even school hours, names of friends, etc.) and not to use your card.
Never allow your children to meet people they met online.
Teach them also to refuse on their own to meet in person with people they have met on the Internet. Explain to them that strangers they want to meet can be dangerous.
Use so-called "filters" which are special software products designed to block access to undesirable sites (violence, pornography).
Check the content of audiovisual material, such as CDs, discs, etc., that your children buy or share with their friends.