Bookmarks are based on a snap judgment so a posting's value has to be obvious at a glance. Here are some influential factors.
1. The headline has to scream "Click me!"
2. Create a killer first sentence.
3. Break the monotonous wall of text with a picture
4. Make the content simple and skimmable by leaving it free of of complicated jargon and long sentences.
5. Put in a widget from a bookmarking service most people already use.