Shares are often highest when information is seen as being in the public interest. Also, try suggesting specific types of friends users might want to share with, in terms of demographics, interests, opinions, etc.
This post got 3,500+ shares. Shares are often highest when information is seen as being in the public interest. (Also, try suggesting specific types of friends users might want to share with, in terms of demographics, interests, opinions, etc.) News consumers do not always give journalists credit for having a public service mission. The trust-building language turned this story from a simple day turn about a food recall into public service information that was helping keep the community healthy and safe. 
Themes:
Watch how users share your posts. Sometimes the best conversation happens on their shares, not on the original post.
Watch how users share your posts. Sometimes the best conversation happens on their shares, not on the original post. Also, questions that are personal or especially controversial work best if your users already are used to talking to you. You might need to build up to these conversations if you want them to be constructive.
Enid overdue bills scam
News consumers do not always give journalists credit for having a public service mission. You can encourage sharing and reinforce your mission by emphasizing how your news is in the public interest. 
Newsy Native Americans
627 likes on a comment! Look for opportunities to explain your process, especially when you see commenters asking questions about it. This comment shows a thoughtfulness behind word choices that not all news consumers would assume journalists have. This example also shows the value of staying involved in the conversations we host and participating in them.