If you are an old time WOW player, you'll be interesting in this Elitist Jerks' article on getting around the five second global cool down timer. This is really important for PvP.
https://web.archive.org/web/20080408033047/http://elitistjerks.com/f47/t15393-global_cooldown/
Here is a more detailed information about the five second rule, including the mana regen formula in case you are into math.
https://web.archive.org/web/20080408013010/http://elitistjerks.com/f47/t15391-five_second_rule/
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