Use someone else’s content – it doesn’t need to be original. Find someone will a strong social following on a social networking service and repost their content on another service using lots of tags.
Ex. Find a popular artist and tweet their picture. Find a quote and overlay it on a picture to share on tumblr.
Use instantly gratifying visuals – use images that inform. Find or make something that people are surprised to learn and proud to share.
Ex. Infographics or “before and after” pictures.
Play both sides of an argument – ask for your audience to engage. Present a black or white situation to your audience and ask for an answer through engagement.
Ex. RT If you love the weather. RT if you hate the weather.
Just ask. Tell your friends and DM people to repost your content. Individually ask people in exchange for something. Or just ask them for a arbitrary favor.
Ex. I’ll give you a cookie if you retweet this. I need you to retweet this, or I will fail my class.