Happy to help, Janna.
1. Email, email, email. It's one to post it. It's another to get it in people's workflow. Like Steve said, set a schedule for posting, but also pick a schedule for sending your posts - daily, weekly, etc. Pick a day of the week, make it part of people's rhythms
2. Images. Include pictures whenever you can. Employees at agency events. Employees in action. Images that represent your mission. Customers / people who are benefiting from your agency's mission.
3. People. Highlight and honor good work. Interview both senior leaders and front line employees. Blog the high points, but also include some rich media, if you can (video clip, audio / podcast - don't worry too much about it being perfect). As Steve said, you could even have others write so it takes the pressure off you and spreads the insights around. If more people own it, they're more likely to promote it as well.
4. Problems. What are the common challenges that you know people are facing? Can you address them in a respectful and constructive way, allowing people to share input on that subject?
I could probably come up with a bunch more, but that's off the top of my head. I know there was another conversation on GovLoop awhile ago (years ago!) on blogging tips, so maybe you can search and find that (on the run right now, otherwise would grab it for you 🙂
Good luck, Janna. Blog back here and tell us how it goes - sharing your own lessons learned!