http://www.wowwiki.com/Four_Horsemen_%28original%29
http://www.tentonhammer.com/node/26652
4 bosses: Ragnaros, Meteor, Green Beam and Void Zone:
Raggy puts fire dot on tank, meteor summons meteor (Stack on tank), green beam you gotta avoid chaining :D and void zone you move out of.
Ok enough with the obvious shit; everyone needs Fire Protection pots here, Shadow too but in all liklehood most of the dmg you will take is gonna be fire.
Tank rotation:
http://warcraftmovies.com/movieview.php?id=124295
This is hard to describe in words so follow these pictures: when you look at them the first time it wont make sense, so have a look at the video then this. Try to follow one tank not lookt at the overall picture
Starter positions;

Transistion one
All the tanks that were idle[E, F, H and G], at the 0:32 second mark start to move in to taunt over. Tanks who were tanking [A, B, C, D] then move to the safe spots ready to move in on the opposite boss (roughly on mark 4 ie 24seconds later at 0:56).

POSITION ONE So after 0:32 its like this:

After 24 seconds, or 0:56, the idle tanks[A, B, C, D] then move in
Transistion Two

Same again, idle tanks [E, F, G, H] move in to the opposing boss, tanking tanks [A, B, C, D] then move to idle positions of the opposing boss ready to move in 24seconds later :)
POSITION TWO 0:56

After 24 seconds, or at 1:20, the idle tanks[A, B, C, D] move in
Transistion Three

Same again, idle tanks [E, F, G, H] move in to the opposing boss, tanking tanks [A, B, C, D] then move to idle positions of the opposing boss ready to move in 24seconds later :)
POSITION THREE 1:20

After 24 seconds, or at 1:44, the idle tanks [A, B, C, D] move in
Transistion Four

Same again, idle tanks [E, F, G, H] move in to the opposing boss, tanking tanks [A, B, C, D] then move to idle positions of the opposing boss ready to move in 24seconds later :) got the hang of this yet? :D
POSITION FOUR 1:44

AND VOILA! We are back to the original positions, 1min 44seconds later. The boss debuffs are 75seconds in duration which means each tank has a 30second leeway (eg if 2-3 taunts resist, you are still fine as long as its 2/3 a rotation, not every boss :D)
This tactic is known as 2 boss rotation for tanks. For dps/healers its abit different and ill explain later. But the key to this fight is having tanks know when and where to move :P
Heres a nice little gif of it:
