On the fight Ji-Kun in Throne of Thunder the boss will spit out green pools from time to time, these pools can get very troublesome and wreak havoc on a friendly neighborhood raid group. Last night during the fight, whilst soaking pools I discovered if you stand in 2 pools at the same time or soak one and then immediately soak another you only gain one stack of the fight-long debuff.
BE WARNED You will collect two stacks of a 20 or so second dot which will hit you hard unless you pop a defensive cooldown, for example on my shaman I used Shamanistic Rage, Astral Shift and my dwarf racial. Dwarf Priests with dispersion and Stoneform can use this to the maximum. (Note: If using a dwarf priest cast stoneform, then dispersion or else you will be silenced and unable to cast stoneform.)
Also I am not saying the aforementioned class/race combinations are the only two capable of doing this, anyone with strong defensives can (i.e. Death Knight with AMS, IBF, etc, Pally with bubble and such, rogues with cloak and feint, and so on)
Oh an another tip this is common knowledge mentioned in most fight guides, but paladins and rogues can clear their fight long debuff stacks with previously mentioned abilities.