Leave comments on popular blogs. Tell people to follow you on Twitter. If they like your comment, then they'll probably follow you. This is a quick way to gain groups of followers, you just have to know the demographics of certain blogs. Otherwise, just post content that is interesting, funny, or entertaining in any way. Use hashtags so that people you don't know will see your tweets. Interact with your followers. The more "companionship" that you build with these people online, the more likely they are to share your content.