Think in terms of expansion and what gets people excited to share news. Different emotions bring out different reactions in people. Someone is much more likely to share something that makes him/her excited about saving money than something that makes him/her sad talking about dead kittens.
There is no trick to making people share your content, you have to create content that the user enjoys enough to share it with his/her friends.
If you have a budget, there is no better strategy than hosting a large event for journalists; if they have fun, they will usually write positive stories. These sources are where bloggers get their topics, so if you have content that they think their users will like, they will reference it.