Many PvP-players idle in cities, waiting for battlegrounds to become ready. STOP waisting your rl-time!
Install BGSwitch, enter the battleground-queues ...
now typ: /BGS ....... to bring WoW into windowed-mode,
feel free to minimize it and do your stuff.
Just in time BGSwitch will bring WoW back to fullscreen, leting you enter the instance. ..... /BGS will always switch mode!

Have a nice fight

P.S: Please leave comment or give bug-report