If I'm not using beryl and some other window manager, I'm often using icewm. It's simple and it works. Most of the config is done by editing files in ~/.icewm (or a global location like /usr/share/icewm). I usually like sloppy focus rather than click to focus, so there are a couple of settings in the 'preferences' file you need to change to get sloppy focus going.
However, in the latest icewm (v1.2.30), they seemed to have changed how you configure the focus model. There is a menu item on the main start menu that allows you to set the focus model to 'Click to Focus', 'Sloppy Focus' or 'Custom'. I tried 'Sloppy Focus' and it mostly did what I wanted, except that in order to raise a window I needed to click on the window border rather than anywhere on the window, so I thought I'd try changing those 'preferences' settings to what I thought should work. I tried setting 'ClickToFocus=0' and 'RaiseOnFocus=0' but making those changes and restarting icewm didn't seem to do much. Then I finally tried changing that start menu item from 'Sloppy Focus' to 'Custom' ... and now my type of sloppy focus worked (ie. moving the mouse over a window activates it but won't raise it, and clicking anywhere in it raises it). It looks like you have to set it to 'Custom' for all the old focus settings in the preferences file to be recognised.
There's actually a new config file for that focus mode start menu item called 'focus_mode'. (eg. ~/.icewm/focus_mode ). If that file has 'FocusMode=0' in it then its set to 'Custom' mode.
