How do I change default program at "Open"

I just installed LibreOffice on iMac OSX 10.9. I also have NeoOffice suite. I want LibreOffice to be the default office suite. In “Open” and “Open With” in the File menu, NeoOffice is the default program so that when I click a file in Finder it automatically opens in NeoOffice. How do I change the default in “Open” to LibreOffice?