How do I open folders in new windows/tabs by default in the Finder in 10.9?
The closest solution is to go to Finder Preferences > General, uncheck the "Open folders in tabs instead of new windows" option, and then use Cmd + double click to open in a new window.
Source: Apple Support Communities - Mavericks Finder - how default to "double click opens new window"?
3 ways:
Close sidebar, right click tool bar in window and "hide". Now you can double-click to open.
Command-click folder
Turn on right button clicking for the mouse in System Preferences. Then right click for sub menu and "open in new window"