What are some good strategies to make a job posting go viral?

Using more than one social medias.. Example: LinkedIn, Monster jobs, Akhtaboot, Indeed jobs, Facebook, etc

Depending on the position you can also seek fresh graduates from universities (Job placement programs, if any) 

You should make it easier to share, using the right tools for that. Use proper hashtags when sharing the job post on social media sites Ask people and friends to share the post. There's huge online portals you can use such as Bayt.com and other recruitment websites.