Google has updated their Google Drive app to allow sharing directly from the Google Drive folder. To share a file currently in your Google Drive folder, all you have to do is right click on the file, go down to Google Drive, and select "Share...". It really couldn't get much simpler than that.
The update is available in both the Windows and Mac versions of the software and will be coming to a desktop system near you in the coming days as it rolls out. Of course, if you aren't already using Google Drive's desktop app, you can download the nifty syncing software directly from Google (source link #2)