EDIT 2012-8-19: This guide is out of date and does not reflect modern fitting strategies and tactics.
As the most expensive ship most players would ever consider flying, and the sub-supercapital the combat abilities of which are most affected by the contents of the cargo, dreadnaughts are uniquely worth fine-tuning. I've been tooling around in one for a couple years now, and having finally found a cargo loadout I'm happy with thought it was time to impart some wisdom. This was originally going to be about dreadnaught cargo in general but turned into a detailed naglfar guide because it's more complicated than the rest.
EDIT 4/7/2011: This is no longer true. Today, supers are the only thing worth flying and dreads are disposable. Gank (close-range) dreads may be used for nyncing, ninja sieging and suicide ganks on e.g. enemy supers which are being tackled.
There are two points on which I don't really agree with my alliance fitting.
First, the capacitor power relays. Flux coils have faster recharge for fast jumping, and also don't reduce shield boost. I think they use relays because the cap lasts longer, but realistically you will never cap out. Lag often means the booster doesn't cycle, and in any real fight incoming damage will kill you long before the two minutes it would take to cap out anyway.
The second point is the dual sensor boosters. A single SB will give you a targeting range of 185 km, and I have only once been further than that from enemy capitals -- which were specifically sniper fit, and we waited for the siege cycle to end and warped to 0 on them. This fit has a serious resist hole in EM, and swapping an invuln for a thermal mod wouldn't hurt either. Most people fly rev and moros, so it's bad to have low resists in em/therm.
Unless you have good reason to believe that you will lose your dread, get basic insurance. Basic runs around 50 mil while platinum is 280, and a capital is a fairly durable investment. I've spent a lot more on insurance than I have on replacing them, maybe even more than I've spent on hulls, and recently switched to basic insurance. Any decent 0.0 alliance should have a capital replacement program, so replacing a capital shouldn't be a major financial burden.
Although fuel requirements will vary depending on what sort of range you deploy to, dreadnaughts can never have enough fuel or strontium. Containers, which have more storage space then their volume, give you a little more cargo space to work with. The nag can fit a giant and a medium container, which I keep extra fuel in.
Generally you want to carry a minimum of 5 cycles of strontium. Six is better, and with the fuel requirements in our fleets 7 means having a cycle left when almost everybody else is out. Ops staging out of tribute typically call for between 20k and 30k isotopes. I like to carry 6 cycles of strontium, which gives me 33k fuel; although I could fit 7 cycles for most ops, I find that having extra isotopes is useful as proof against minor fuel requirement mistakes, plus the spare can be given to the inevitable person who finds out he's a little short for the return trip.
720 rounds (18 reloads) of faction artillery ammo is enough to fire continuously unlagged for almost 1.7 hours. Ammo is chosen for damage types -- carbonized lead (long range) and depleted uranium (medium range) spread damage types the most in their ranges, while at close range EMP and fusion allow us to choose damage types for shield and armor tankers respectively. Although this gives us twice as much short range than medium range ammo, and althogh capital fights usually occur at medium range, 720 rounds is far more than I anticipate ever using in a fight.
Combat missiles have the same damage type considerations, so I have selected thunar (EMP) and catastrophe (explosive) for shield and armor tankers. 360 missiles will last slightly longer than the 720 rounds of artillery ammo. Missiles have only one range and there are no faction citadel cruise missiles, so our missile selection is simple compared to projectile ammo.
Faction explosive ammo is loaded at all times when not actually bashing a structure. You do NOT want to try to reload after jumping or undocking into a laggy fight.
Ammo (structure bashing):
This always happens at close range, and it's not worth switching ammo types to try and find the resists. Because I spend a lot more ammo on a typical structure shooting op than in a typical capital fight, I carry twice as much non-faction close range ammo as I carry of each type of combat ammo. This number is used because it is more than will ever be needed, plus it makes balancing pos bashing missiles easy. I don't actually anticipate structure bashing at long or medium range, but carry a few units of medium and long range non-faction ammo anyway because we have a little discretionary space for unexpected situations.
With missiles, I use thermal or kinetic. This is so that I don't use combat ammo to shoot a pos and find myself out of the correct damage type during a fight. Like projectile ammo, twice as many pos bashing missiles are carried as each type of combat missile.
A word on side effects -- standard boosters have a 20% chance of causing one of their four possible side effects. With nanite control 4 this decreases to a 16% chance. At most one of the side effects per booster will be meaningfully detrimental (i.e. decrease maximum hit points) so you actually have a 4% chance of getting a bad side effect.
Blue pill: Increases shield boost amount. One of the side effects is reduction in maximum shield capacity; however, one suspects this would work like a gang booster leaving, so if you have more than 20% shield damage it would not remove any existing shield HP.
Drop: Increases tracking speed. Has a chance of reducing shield capacity, so it should ONLY be used when you are confident there are not enough enemy capitals around to kill you. Generally this will be used for shooting subcapitals.
Frentix: Increases optimal range. This has a side effect of shield BOOST penalty, which between lag and the high incoming damage will rarely significant in a capital fight.
Drones (not pictured):
I carry one flight of sentries, one of light ewar drones for idiot-proofing and the rest light combat drones. The nag has 225 m^3 of drone space, so unfortunately a spare flight of sentries is impossible. Drone control range is around 60 km with decent skills, and enemy capitals are rarely under this range, so I recommend using sentries with an optimal around 50 km.
Make it a habit to refuel and reload immediately after returning from an op. Check all your storage spaces - fuel, cargo, containers, drone bay - to make sure that nothing is missing. And for the love of god, make sure that your siege module is set to auto-repeat OFF. The truly cautious will split their strontium into stacks of less than one cycle so the module fails when accidentally triggered. I don't do this because I'm lazy.