Over on the Noodlesoft Forums for Mac OS X automation utility Hazel, I found this basic sync recipe for setting up a folder sync. Sometimes it’s easier to get going with Hazel when you see an example.
This one was created by the developer, so you know it’s correct. I was looking to set up a sync for my personal art projects, where anything created in the last 6 months was synced to Dropbox for easy access on multiple devices. Works great.