Social media covers many different types of communication techniques. You may need to start by narrowing your topic to one particular application of the technology since social media could include
Internet forums, weblogs, social blogs, microblogging, wikis, podcasts, photographs or pictures, video, rating and social bookmarking.
You also need to determine your topic regarding that type of media. Do you want to support use of one of these media for a particular purpose? Do you feel there should be censorship, or at least more supervision, of posts? Do you think that the media you have chosen is changing the way people interact for better or for worse?
Once you pick your application for the focus of your research, you need to gather your information. Locate statistics regarding numbers of users and how those figures have changed over a period of time; find out the age group of most frequent users; if you can obtain information about the amount of time users spend with the media, that would be worthwhile data to have available.
Your first point in the body of your essay should explain exactly and fully what is involved in the particular area you are examining. Your second point might present the statistical information you have found regarding how the use of this social media is changing and affecting the lives of its users. Your third point would examine the meaning of the data - how the use of the social media is impacting the lives of users, the general culture in which it exists, or other impacts depending on what you have presented earlier in your essay.
If your essay needs to be 6-8 pages in length, you have the opportunity to develop this topic with a good amount of detail. It's a very timely assignment. Good luck!