Too much sensationalism causes you to lose credibility, but if you are starting with none then you might not have much to lose by testing different things. Take this post, for example. Let's analyze it.
The person who wrote the story about Google submitted it to the Apple category.
The post is half-assed research, passes opinion as fact, and is completely wrong in it's conclusions, but
The post is titled Google's dirty little secretThus despite multiple layers of ineptness it is passed off as good information based on the title alone. It made the Digg homepage. A good linkbait starts with a good title.
Need help with your headlines? Go get some magnetic headline love.
Another tip is that for the amount of effort you need to put into making a piece of information, you are typically going to get much more out of it by making it biased than by aiming for vanilla. Your bias is what people subscribe to, want to believe in, or want to discredit.
For example: I think Iraq for Sale is a film every American should see, largely because those who allegedly support a free market system think that the uncontested multi-billion dollar government contracts full of fraud sent to scumbag corporations are an acceptible business practice. And they only get away with it because people argue on the rhetorical or idealistic levels instead of talking about what is actually happening, and the media is generally not honest enough to report some of the news themselves...they are too tied to profit to allow themselves to.
I bet someone comments about that last paragraph ;) Also notice how I lined out I think. If you want to be controvercial an added way to do it is to present opinion as fact, but be forewarned that if you go to far with that it makes you an easier lawsuit target. But if you plan it out correctly lawsuits can go right into the marketing budget. With some stuff it almost seems like that is how Google does it :)
Linkbaiting is all about emotional reaction or being memorable...that is what leads to comments and citations.
So how else do you make your story comment worthy or citation worthy? You build up a following over time. Those who read your site may Digg, Netscape, or Del.icio.us your posts.
How else do you do it? Have an instant messenger list a mile long, and email. Beg your friends. Time your post, bookmark your site, and then light up contacts via email and instant messenger.
There is not a lot to the linkbait formula time your post for a launch when your friends will be around, use a catch title, Digg your own post be really biases, or format your information so that it LOOKS fairly comprehensive beg friends make it easy to bookmark your page by placing buttons on your site.