I would start with brainstorming.
1) You can ask a general question about their hobbies and try to get the answer "computer games"
2) Once you get that answer, you can make use of a graphic organizer to make a list of disadvantages of using internet and computer games.
3) Then, maybe you can show a short video which reflects the bad effects of internet and ask your students which of the disadvantages they mentioned can be found in the video.
4) You didnt mention the type of the writing piece, but I guess it is an essay, so if your students are familiar with essay writing, you can quickly go over the format of an essay and ask them to write one based on the facts on your organizer...
If you want your students to work in groups, here is my second suggestion.
1) You can start with showing two short videos. One showing advantages and one showing disadvantages
2) You can then ask your students to work in groups and give each group an envelope with slips of adv and disad. of internet. You can ask them to seperate them into two groups so that they can have their lists in front of them in the end.
3) After a short class discussion, you can tell them that today you are going to work on bad effects and introduce the writing piece they are going to write...
Good luck!
