First off, this is a combination of a few things I've seen around the site. This works really great for pretty much everyone but it works even better if you have the ability to stealth.
To start you will need some sort of program that hits one of your keys periodically. I use Iwana FishBot since I enjoy fishing in WG all the time. Iwana hits my '1' key for me almost every 15 seconds which is also my fishing macro button.
Next you will need to setup this macro
If you are using Iwana, place the macro in the '1' keybind.
Next find a good hiding place where you think action is going to be and open Iwana, go through the motions of picking a pixel color etc.
Zoom your camera in all the way to the ground and hide your UI so there is none of that color on the screen.
Run Iwana, Iwana will try to find the color and repeatedly cast your fishing macro in the process. When the 15 minute mark comes up the dialog box for Wintergrasp Q'ing will pop up and it will automatically hit yes along with add you to the group when the game starts.
On my druid I tend to stealth somewhere high in the pillars of the fortress and farm marks, but on my priest where I can't stealth I just sit around and actually use the bot/macro to fish which usually that only yields one mark because I am so far from the action (but still get tons of hours in fishing).
Anyway, farming marks/farming fish, this should prevent you from missing the q. Sometimes you will not be accepted when the q finishes, which kinda sucks. So using this at off peak times is ideal, also works well on lower pop servers.
Apologies if this has been posted, I searched and couldn't find anything related to it.
Edit: Also, I apologize for posting a macro, I just read the rules. Though I wouldn't really consider this just a macro and it doesn't feel like it should go in the Macro forums.