Would someone please explain how Focus is supposed to work?

I have an instant message program, and I want new chat windows to pop to the top of the desktop and take focus (otherwise I tend to miss them).

I've tried playing with Window-Specific settings in Configure Window Behavior. I create a New Setting (if that's what it's called) for the window, and in the first tab, pressed the Detect Window Properties button and selected a chat window. On the Preferences tab, I've selected "Accept focus", "Force", and checked the (unlabeled) box after the Force listbox (what is that, anyway?). On the Workarounds tab there is a "Focus stealing prevention" list box, but I'm not sure what I should set it to.

How should I set these to get what I want? How does Accept-focus and Focus-stealing work and affect each other? There no Help for these settings that would explain all this.

Try changing "Focus stealing prevention level" in System Settings > Window Behaviour > Window Behaviour > Focus to None.