Hype - Hip hop icons Public Enemy famously rapped "don't believe the hype," but people don't have to believe what they read... as long as they are reading it! "Lose 10 Pounds in 10 Days!" It has a hook and may just be a little unrealistic. But it may work as link bait.
Controversy - The tabloids perfected it. Now, anyone with a website can create controversy (hopefully avoiding legal liability) in order to drive traffic to their content. But you don't even have to create the controversy. Just share your thoughts on a controversial subject (Politics, Religion, etc.) and you can generate discussion and link sharing.
News - You don't even have to hype it up or stick to controversial news. If your news is fresh and interesting, there's a good chance people will share your story with their friends. But even if you are re-blogging about interesting news from a different website, people are apt to share your post with other people.
Humor - What makes people happy? Laughter. By its very definition, laughter occurs when people are in a happy mood. Sure, I guess there is technically nervous laughter, but you get the point.
When people find something on the Internet that makes them laugh or smile, they will often share that experience with their friends. All their friends. And maybe even mom and dad. That means a lot of potential eyes reading your humorous content.
Interaction - Promote interaction. Facebook does it all the time. How many times have you gotten an email from Facebook saying that a friend took such and such quiz testing their movie knowledge inviting you to take that same quiz to compare results? Or maybe you have a friend who participated in a poll? If you offer something that allows people to share their thoughts or learn more about themselves, they just may want to test that on their best friend.
Quality content - With all the tricks and underhanded sneaky ways people may try to get you to link to your website, what's better than providing good old-fashioned quality content. If you are blogging about a topic that has an audience, even if it's a small niche, and you are doing so in a thoughtful, interesting manner, there's a good chance that your readers will take the time to forward your posts to friends.