That is all up to personal preference honestly, as far as skills go, unless it's when/how they are used, there's no real guidance. Because where they are, if you can still use it properly, is not a big issue. On my alt dgdggdg hghghghg I set up crossbar 9 for pet actions, just so I could see if it's skills were off cd, will do the same once I get the jobs on it.

The best thing though, is to place them on a cross bar so you can see the cd, like above poster mentioned