In the 10.7/10.8 Lion/Mountain Lion days of OS X, installing developer/command line tools for xcode involved opening Xcode, going to preferences, and installing from the additional downloads menu.
In some ways, it's actually a little easier as of 10.9 Mavericks. Just enter the following in your terminal:
I've had some problems with the above line, occasionally their servers seem to be down (or not pushing out updates).
In that case, looks like you can grab the DMG from here: https://developer.apple.com/downloads/