How to Unstick a Stuck Mac App Store Download

Periodically you may try to install/download/update an app in the Mac App Store (MAS) and it will sit there "waiting" indefinitely. Restarting the MAS doesn't seem to help. What did work for me was the following:

1. Quit the Mac App Store.
2. Navigate to /Applications/Utilities/
3. Open Activity Monitor.app
4. Search for "storeagent".
5. Select it, choose "Quit Process".
6. When asked if you really want to quit the process, choose "Quit".
7. Open the MAS and try to download the app again.

Note: Before you do this, you can also try holding Option, and it will give you a chance to "Cancel" the download, but this didn't seem to fix the issue for me.