Is there any "rule" in installing window managers? I mean for example installing xfce4 and kde.
I wand to run apps which requires kde in xfce4.
Is there any specified order in which install wm? does it matter if I isntall xfce4 at first and then kde or otherwise?
Respect is everything 8)
Nope, doesn't matter. Dependencies are automatically fullfilled when using pacman.
you shouldn't have to worry about installing kde. the beauty of pacman is that you can install xfce, and then install any programs you want and their kde or gtk or whatever else dependencies will be fulfilled. so unless you're planning on using the actual kde desktop environment, i'd go with not worrying about it and install specific app's dependencies.
by the way, your ambiguous thread title probably isn't good practice. you should try to be more specific about the problem so people will get a general idea before they click on it. for all we know, WM might not even mean window manager