Include files from secondary hard drive in spotlight searches I have an SSD as my boot partition and a HDD for all my documents on my Mac (OS X Mavericks). 
I have noticed that I am unable to search for files on Spotlight that are located on my HDD.

I suspect they are not being indexed as they are not on the OS drive. How can I include them?
All hard drives (both internal and external) can be searched though Spotlight. It's possible that it may need to be re-indexed.

To do this, go to System Preferences > Spotlight, then click on "Privacy". Click on the "+" button and select the hard drive that you wish to re-index. After that, select the hard drive within the Privacy list, and select the "-" button.

It should start to re-index the hard drive in question (you should see a progress bar in Spotlight when you click on it).