Well, as a Horde, I can give you tips from the opposite side of the spectrum. That said, *shakes fist,* WHY SO MUCH HATE FOR OUR LEADERS?! ;D But yeah, I think half of it is getting a good group together, and the other half is the element of surprise, and keeping it quiet during the raid--and by "quiet," I mean the amount of attack messages your raid spams, so kill only what's necessary. Anyway, here's some ideas you might consider:
1. Do it at an odd time--if your server's big on Tol Barad, try getting your raid together a half hour or so in advance and waiting at Thunder Bluff until Tol Barad starts. Coordinate your raid to start AS Tol Barad calls. The later at night/morning, the better, but you'll have to balance the ability to gather raid members with the enemy's ability to gather a defense. If you know you can pull a raid together at 4 am, that's awesome--do it.
2. Thunder Bluff is pretty quiet. It takes Horde awhile to get there, and often, they just don't bother. That said, the bosses now take a long time to kill. Station PvPers around the outside to stop PvP interference. That means that they can dps the boss, but their priority should be to stop problems before they start. For example, if a mage starts casting Poly on your tank, your PvPers should be ready to take him out.
3. Have as many core members on voice chat as you can, for coordination, especially on the PvP side. Healers should know when to cleanse incoming CC off the tank, as otherwise Baine will then wipe the raid; having two offtanks for this is a good idea, just make sure they stay at the top of the aggro table. Voice chat will also allow you to coordinate AoE healing or shielding in the case of a Horde say, spreading a very nasty Combustion throughout your entire raid. You can also rotate mana returns--Mana Tide and Innervate, Hymn etc. If you don't have voice chat, consider making /raidwarning macros in advance.
4. Be unobtrusive. No /yelling, no killing guards that haven't aggroed. The raid should land in front of Baine--OUT of range--and quickly deal with all NPCs that summon guards. The fewer "Thunder Bluff is under attack!" messages you trigger, the better.
5. If you PuG members, don't tell them exactly when or which city you're doing, if at all possible. Spies abound. Keep someone with Have Group, Will Travel in Mulgore, and tell them to respond to any questioning /whispers with "I'm trying to get the Thunder Bluff flame." Or, keep a lock + two people in an adjacent zone, to move into Mulgore only as the raid's about to start. Regardless, keep them *out* of the raid until it's time to start. If you're advertising in /2 for people and telling them when and where you attack, hordes of Horde may very well be waiting when you arrive. Also if a spy joins the raid and sees a lock + two people in Mulgore, they're going to know what to expect.
Obviously, you need a good couple of tanks, quite a few good healers and plenty of dps; the bosses have a ton of HP, and mana may become an issue. Baine is, however, the easiest of the lot--the easiest to get to, and one of the more distant for Horde to defend. Since you're doing it during the Fire Festival, too, the attack messages that you trigger might be taken as "someone's getting the Fire," unless your raid gets out of hand and wipes a whole rise before the raid.
Oh, and ReadyCheck before you start >.<
Hopefully some of this helps! Remember, it's all in fun, and more often than not, these raids fail anyway... and people don't care, because it's almost always really fun regardless.
Good luck!
(I can't believe I'm saying that to a FTA 
)
). Also, just a random tidbit here, but someone in our guild who's level 50 signed up for it... >.>;