As far as i can tell Mist Howler is on either a 12 or 24 hour spawn time (most likely a 24). to tame him i set a freeze trap backed up and started to tame the only problem being the fear ability which caused my failure and death several times but you just need to be lucky. as far as macros go which there were some questions about all you need to do is press the Esc key and select macros from the options, select the icon you want and type the name such as mist howler then in the window below type /target mist howler and you are done.

good luck and happy hunting