Raiding in WoW leaves a player with a huge number of details to keep track of.
Since I've been serving as the Raid Leader for our 25-person stuff, I find it simply staggering how many details we need to manage. And its usually 4 seconds before the boss attempt is about to begin that I realize I forgot something.
You've got some that happen way in advance of raiding, such as getting the right gear with the right stats (1), and remembering to get the right enchants (2) and install the right gems (3) with the right stats, but don't forget to fiddle a bit to keep your Meta gem requirements met (4), put some leg armor upgrade in there (5), and grind the right dungeons (6) to get rep with the right factions (7) for the right shoulder inscriptions (8) and helm glyphs (9).
Then you've got some details to manage shortly before a raid, each night. Log in at least 30 minutes early, taking note of your Server's silly timezone (10), get your repairs (11), empty all the stupid stuff out of your bags to make room for phat lewtz you're gonna get :-) (12), fill your quiver (13), get your foods (14), elixirs (15), flasks (16), drums (17), potions (18), bandages (19), your pet foods for happiness (20) and DPS (21), pack your trash gear (22), your +hit gear (23), your stamina gear (24), your oils (25), your scrolls (26). Other classes have shards, area wide buff consumables (candles???), sharpening stones, on and on and on.
Then you've got the things you do right at the beginning of the raid, and also after each wipe. Eat your buff food (27), feed your pet to happy, feed her again for good measure (28), feed her a Kibler's Bit (29), check you've got the right Pally buffs (30), the Priest buffs (31), the Druid buff (32), [edit: oye. I forgot the Mage buff, but no way I'm renumbering this whole thing, sorry Mages] drink your guardian elixir (33), drink your battle elixir (34), or check that your flask isnt about to expire (35), reapply mana oil if needed (36), eat a mage biscuit or Naaru ration to health and mana up (37), make sure the right Aspect is on (38), make sure you have the right player focused (if you indeed use focus for anything) (39), make sure growl is turned off (40), make sure pet is on passive (41), make sure your riding crop is safely stuffed in your bag just in case Outfitter went crazy (42), in fact, just check over your whole set of gear to be sure you're not still in that BG or Fishing set (43). Don't forget to grab some mage food (44) from the table and grab healthstones from each warlock (45).
Then you've got the details you need to manage during the raid. For the moment, put aside the details you need to keep track of for the specific boss fight, and just think of the ones you manage for your own toon. Lets consider a Beast Master Hunter in a basic tank-n-spank fight:
Before the pull, make sure you have any encounter-specific macros loaded on your action bar (46).
Start with the basic threat meter. Gotta keep your eye on that little puppy, first and foremost (47).
Along the lines of threat, you gotta manage your Feign death cooldown timer (48).
And your Misdirection cooldown timer (49). And you better make sure you cast MD on the right player (50), and then fire your shots at the right mob (51), within the 30 second timer (52).
Details details details.
Good, your tank has some solid aggro, and your FD was just successful (resisted FD, FTL), so now its time to pour on the juice. Gotta be aware of the cooldowns and availability of your Bestial Wrath (53), Bloodlust Brooch (54), and Rapid Fire (55) here.
And if you're a drummer, better remember to play them from time to time (56).
Do you have Improved Hunter's Mark? Better remember to keep that puppy up (57). Lots of lost DPS if you let that one expire.
How's your mana (58)? Better remember to manage your potion cooldowns (59) properly. Or if its real bad, flip over to Aspect of the Viper for a little while (60). But better not forget you switched, and remember to turn Hawk back on (61).
While you're looking at your mana bar, maybe glance at your health (62). Time to manage the Bandage cooldown (63), the Healthstone cooldown (64), and any other health or stamina related consumables you use (crystal charged green hexagon thingie???) (65). And if your mana was OK, maybe try a Health Potion (66).
Building up the pressure, didn't you just hear a Bloop recently? Yeah, that's Critical Alert telling you about a crit, so instruct Rover to Sick Balls (67). But that's like a Pavlov Response, or maybe automated in a shot macro, so this one might not require too much thought.
Speaking of Rover, he's a tough puppy, but better monitor his health level (68) and make sure Mend Pet is ticking (69, lol) if needed. If the situation is really dire, you might recall the pet (70), let a mend or two run its course, and then you gotta remember to send him back into battle (71).
Now, how about if you're the raid leader? I'll just go high-level on this one, and avoid the specifics of any specific boss fight (Cube Clickers, FTW)....
Better make sure you have 25 folks ready to raid (72). Of the right composition (73) for the fights you'll be doing (74).
Now you gotta get the parties right (75). This one alone could be like 50 details, but I'll just simplify and give it one point.
Set the looting policy to Loot Master (76) and specify who your LM is (77), assign two assistant raid leaders (78), set the loot level to Rare or Epic (79), however you fancy.
Make sure everybody knows their job (80). Make sure you review the looting policy incase of any visitors from other guilds (81). Make sure you've assigned a Healing lead (82), Tanking lead (83), Pally buff lead (84) (to hush up the coconuts who are nagging about not having the right blessings), Hunter Misdirection assignments (85), know who has soul stones (86), know the status of each Druid's combat rez cooldown (87), make sure you've got everyone on vent (88).
If you just wiped, or just killed a boss, better be aware of the time (89), and decide if you're going to make more attempts/push further, or call it a night.
Everything else I'm thinking of that I do as Raid Lead gets more into the specifics of an individual encounter, but you can easily double the number reached thus far.
I'll go with a few generics that're common to just about all fights: keep track of the overall health of the main tank and be ready to call out for the backup to step in (90), monitor the overall status (alive or dead, or maybe even mana levels) of your healers (91), keep track of your general raid DPS progress against any enrage timers (92). Keep an eye on the total raid health and alive/dead status, and call for a wipe if necessary (93).
Oh, boy, and if you're lucky enough to be the Loot Master (I am not, I personally make sure that the GM gets to handle that lovely responsibility), you've got to manage (94) any DKP, random rolling, and distribution of epics.
And if you're the designated Disenchanter, maybe you've got some crystals or shards to hand out (95).
And back to raid leader, you're disbanding now, make sure you thank everybody for coming (96), and give out homework assignments to let the team know what bosses they need to research for next time (97).
Almost ready to go to bed. But not quite yet.
Better remember to run the WWS report (98). You're a Beast Master, so take a moment to stroke your ego at the top of the meter (99). Then review the other Hunters to see who you need to yell at for not casting Kill Command or missing too many shots (100).
Anybody else exhausted yet? Its no wonder why I collapse at the end of a raid.
And, just to make the number come out nice, don't forget to log into your AH mule and leave an Auctioneer scan running (101) before bed.