Black Mage Strategy

"With great power comes great responsibility."

Basically, that's the idea with black mages. You have enough mana to kill a DC or EM monster (or more?) even at 75. You can't just dump it all out, however, or you'll be killed and out of MP after one fight. (See also Soloing, below.)
In a party, the Black Mage balances their power output and mana regeneration, their damage dealing and hate control. Most of the time you want to achieve the ideal balance so that you don't quite get hate, don't run out of MP, but things still die really fast. On top of this, you often have a lot of other useful spells you should be ready to use should the situation for them arise.
At first glance Blm seems like a power-trip job to many, but this is not true. The best jobs for "rar! kill! bash bash!" players are probably Monk, Samurai, and maybe Warrior or Ranger. The best black mages are more likely make from careful study of all the spells available combined with a lot of experience finding out which are really best to use in the plethora of situations that can come up in FFXI.
Well, except for doing the Dawn BCNM with 18x Blm… that's a "bash bash" case maybe… but you only get to cast 1 spell. If you think about it, that's really the result of cunning and careful planning where astute blm players realized a potential use of their spells and capitalized on it. Actually doing it takes good timing and team coordination which are also not "bash bash" qualities.

Cracking the Spellbook
In the early levels a blm mostly wants to cast their best dmg spell on wimps and maybe finish them off with a few wand smacks. Don't go for bigger targets until you really have to. It's more efficient to one-shot weaker enemies with a single spell than waste MP healing or waste time meleeing harder foes.

You can spend a large percent of the way to 20 soloing worms. Duo-ing is best if you can team up with another mage or a Rng. Maze of Shakhrami offers great 13-17 targets, and Korrolokka Tunnel is great 17-20, with Qufim for levels 19-22 (but be careful of the giants and wights). Drain is one of your best early spells, and you'll want to put "/recast Drain" into the macro so you can constantly check when it'll be ready again.

25 and up
You'll ahev the full set of "blm debuffs" by 27: Burn, Shock, Choke, Rasp, Frost, Drown.
The combinations that "stack" are:
Burn Shock Choke
Frost, Rasp, Drown
Frost, Shock
Burn, Rasp
Drown, Choke
Conventional wisdom is that you cast FRD if you're the only blm, and BSC if there are 2 or more blms in the party. It'll be up to you to adjust to the party, of course. Aspir is learned at 25, and on anything you can drain MP from, you want to cast this as soon as the timer is up, unless your MP is full.

• to be completed soon...

50 and up
You get your first Ancient Magic, Freeze, at 50. This opens up the possibility of the AM burst and the Manaburn party.
To burst AM, you simply have to "lead" the skillchains. Make a macro something like:
/ma Freeze <t>
/p Casting Freeze, get ready to Skillchain...
/equip main "Ice Staff"
/wait 8
/p Start skillchain NOW! <call1>

I think 8 is right… was it 7? well you can experiment a bit to find the proper wait time. It also might depend a bit on the response speed of the melees.

How to Manaburn
An entirely different set of skills is required for manaburn parties. At first, they might seem really easy, but you're not getting the full benefit from them if you slack off.
You're party will be 5blms and a brd or rdm. The Brd/Rdm is the puller, and their next most important duty, as you'd expect, is to MP regen the blms. Third they sleep the mob and last they heal you.However! This does not mean you shouldn't help them out. The blms can also heal each other (and esp the Rdm/Brd if they need it), or pull if they have full mp. Stun makes a great pull spell.
Often, the blms are on sleep duty, and with a rotating schedule (alphabetical is fine) you can have elemental seal ready on your turn. Just having all 5 blms cast sleep2 and hoping one sticks is another fine method. For blms, here are tbe manaburn tips:

• one blm should help time casts, party chatting the seconds number on the clock is a common method. Once the mob is sleeping the leader says "45" meaning you hit your Freeze macro when the clock reads XX:45.
• Never use DoT spells. You need to be able to sleep the thing.
• Stun after you finish your Freeze, at least one of you should cast stun. You can elect someone in particular or just have "whoever finishes first" do it. It won't be a big waste if 2 or 3 of you stun it, and it might save someone's ass.
• If it's not dead yet, cast a faster spell to finish it.
• At higher levels, stoneskin is a good idea.

Back to that first bullet point: Cooridnation is they key to a manaburn party. If things get a little out of whack and you have a monster trying to kill you with say, 25% health left, you need 3 blms buring it and 2 helping to keep you all alive. The best picks for which 3 and 2 depends on who's got hate, how much MP you all have, etc. It might be best just to assign the duties ahead of time - most of the time that'll work out fine, I think. Better to do that than to hope strangers can figure it out on the fly before someone dies. (If you have a static burn you'll be able to let people handle it on their own, since you'll get used to each other and start to anticipate each other.)
Similarly you can set stun orders and all sorts of other coordination elements.
All too often in any pick-up party no one says anthing about coordinating spells or abilities beyond a skillchain or sometimes a trick attack setup. For a manaburn party, which has such a high potential if done right, it will be worth the 5 minutes of discussion to set up your teamwork.

Manaburn Priority List
Here's a suggestion on how to coordinate a manaburn party. This system may be adaptable to Dynamis or other situations where a large number of mages must coordinate their tactics.

Each player is assigned a priority list. When in doubt, that player checks the list and accomplishes each goal in order, if possible.

Manaburn
Blm 1
Back-up sleep
Deal Damage
Stun
Heal

Blm 2
Back-up sleep
Stun
Deal damage
Heal

Blm 3
Back-up sleep
Deal Damage
Buff
Stun

Blm 4
Heal
Deal damage
Stun

Blm 5
Stun
Heal
Deal damage

Rdm/Brd
Sleep
Heal
Debuff
Buff

Player 4, for example, above, keeps and eye on HP. If (after the initial AM casts, or if the sleep doesn't stick), someone starts getting pounded, they'll heal them. If everyone is okay, they go to the next priority on their list, and deal some damage. Blm 5, on the other hand, always stuns first if they can.
That's just an example, and not meant to be a tested suggestion on what the actual priorities should be.