Vary Your Usernames
As you register for various social networks, web forums, commenting networks, and chat systems, use a different username for each of them. If your username is Dragon303 on one system, a stalker or investigator will look for “Dragon303” on other systems. This will enable that person to collect and collate more of your information.
If you keep the different networks compartmentalized, a breach of privacy on one network will be less likely to cause a similar privacy breach on the other systems you use. Whoever is looking into you will have a much harder time mapping all of your online activities.