The ability to absorb huge amounts of information from multiple sources and make decisions with what you have.
Large fleets often have 4 or 5 scouts, I often delegate one player I know and trust to relay intelligence from our regional intel channels.
I often ask someone with quick fingers to type up commands given into fleet chat, especially as the fleet co-ellesses or pre engagement. I hate calling primaries personally, having experienced players helps here, because a good wing commander will control everything for you.
Pre fight, call your marks, get as much scout intel as possible, if we are engaged blind, I tend to call a bug out and a re-form a couple of systems over ready to press the engagement again. In the calling, you give clear instructions to your wing/squad commanders. EWAR your targets are Other EWAR, Logistics, Primary Damage Dealers. Spread your Jams call yours amungst yourselves but make sure logistics are neutralised.
DPS concerntrate on Logistics & EWAR, target tackled ships first focus fire on Wing Commanders lead
etc, this way, you utilise EVE voice wing/squad voice channels so you can break your fleet down into more manageable chunks. Large fleets in particular suffer from Large command paralysis, give the control to the commanders and you deal with overall battleshape, let them call primarys and lose their voices :). I often sit in a command link ship in a safe in an engagement, listening... asking scouts for information on my voice channel in eve listening for intel on additional enemy fleets trying to box us in...
Teamspeak is usually eerily quiet during an engagement.
If you have no confidence in your squad and wing commanders, because you haven't flown with them before or for some other reason you will have to do it all yourself, this is ok, but can lead to information overload, this is better with smaller fleets rather than CTA size 300 man fleets.
- Everything the others have said is important also.
Would like to re-emphisis having good Scouts the number of times our fleet has won or lost due to good or bad scouting I can't keep track of. Knowing enemy numbers, Composition. Providing warp ins, bug outs, caught a re-enforcement fleet 2 jumps out meaning we could escape... They really make the difference.
One Last thing a good FC really needs to have.
I have on a few occasions been with an FC who changes his mind.... DO NOOOOT do this, don't hesistate be sure on comms even if you are not in yourself. Not only does not being sure reduce moral, but you will lose combat coheesion.
For example on one memorable run, we were about to engage a Drake on a Gate, this wouldn't have been to much of an issue by itself, but then we saw a slipnier landing on gate. The FC called jump jump jump at a time where half the fleet had aggressed and the other had not, all of a sudden the fleet is split in two and no-one knows if the Drake engagers should de-agress and follow after timers or what. To make matters worse, the slipnier calls in local for help and a dozen enemy ships turn up and point one of the logistics. The rest of the fleet jumps in to help the Logistics as timer depletes, the logistics tank breaks. instead of fighting or running, the FC calls bounce, so everyone picks a planet and warps... 3 or 4 people break teamspeak silence and say they are pointed... so the FC calls everyone back to the gate to help the straglers.
Bottom line nearly the whole fleet was wiped out by a fleet a third of its size due to that one call, this is what indecision can do.
What I would have done, or with hind site perhaps the "Correct way" of handled the Slipnier is the following. Firstly, let it go, you have committed your force accept what this means and persecute your current target, don't get sidetracked by shiny ships like a magpie, it could have been an elaborate ruse or just an accident on the enemy's part but it can splinter the fleet.... Think before giving orders and don't fly by seat of the pants where possible, a rear scout here would have given you the knowledge that a target was approaching and information is key to sucess you may well of been able to bubble the gate and gotten both on this side of gate or at least known a better target was coming and all jumped through to get the better target. If on the other hand you do get into the situation described above then don't divide your forces.
if you really want the second target you have two options, ask a scout to keep tabs on it and once you have dealt with the first regroup and then pursue when all are clear. Other option is to ask a scout to point it in the next system and hold it till you can jump. Option 2 is clearly the best but is far more risky to the scout... Deoends on what you have scouting you (inty or Cov ops) and goes back to having experienced and decent scouts.
Another possibility is having dictors to bubble incoming gates, but this is again dependant on fleet composition, but if you have them use them.
Also this is clearly an offensive camp, if you are in a defensive camp or even worse a dedicated CAP don't even think about pursuing.
At the end of the day good FC's are developed by experience, skill and intelect are just as important, as is natural ability. However nothing can trump knowing your enemy and knowing what all the ships in eve can do, and practice, practice, practice. Which is a catch 22 of course, because most people only want to be with a good FC, therefore there will not be good FC's. Start with small disposable frigate roams and learn on the job. One of the best FC training mechanisms I've known in alliances are to have a fleet taken out once a week by a complete unknown FC (a junior if you will) fleet is 20-30 people, nothing bigger than a cruiser, no expensive fits. The ships must be losable, as the FC is instructed to be out for a fight and will almost suicide the fleet on purpose to gather vital battlefield experience. It is Fraps'd and then debriefed afterwards by experienced FC's and then they get on TS with the FC's and explain the mistakes made and how you can avoid them.