Why are my menu bars always on my left monitor? I have a Macbook running OSx and have two external monitors plugged in. Unlike for all my colleagues, whichever app I use, in whichever monitor, the menu bar will always be in the top of the lefthand monitor. 

This is obviously very annoying when using an app in the right-hand monitor or Macbook screen.

How do I get menu to appear on the same monitor as the app? I've found reference to something called Secondbars but supposedly the need for this was going to disappear in Mavericks.
It depends entirely on one pref...

System prefs > Mission Control > Displays have separate Spaces.



This will, however, completely change other aspects of your workflow.
The dock will always be present on each screen; you can no longer use screens in pairs, each is independent, so changing Spaces on one screen doesn't take the other with it; you can't have the same Space on both screens at once, but you can invert the left/right order of Spaces by swapping each on the other screen, via a 3rd Space.

Personally, as you can probably tell, I hate it ;-)