[dirtyclown]

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Parties and you: A guide for the somewhat retarded.
Just kidding about the retarded part. Anyways, as you know, your #1 priority is to keep hate. How you go about that is up to your party. Always ask what the Skillchain will be, and if your party is unsure, then you have 2 choices. Help them figure out one by googling Dranok's Skillchain calc or using one of the many charts, OR running like hell. Because a party that doesn't know what SC they want can be detrimental to your health.
One other thing to note is this:

The really good PLDs know how to keep just the right amount of hate for letting melee turn the mob for SATA, but not lose hate to big WS or MBs.

Hate can be approached two ways. You can either dominate it completely, which basically equates to you spamming JAs whenever they're available and constantly Flashing in order to prevent disaster, or the laid back approach. Knowing when to use different JAs, when to Flash, and when to let the melee turn the mob. Sometimes we need a breather, and sometimes we need to let the Thief SATA onto us. Whatever the strategy might be, you will need to learn how to do this. In time, after you have tanked long enough you will learn what you can do to keep hate at a reasonable level. When that time comes, you'll be a much better Paladin for it. One other thing to remember is that just because you lose hate, does not mean you're bad at your job. Losing hate happens, it's not something you can prevent and that's why total domination is a flawed tanking strategy. It's always good to have a few aces up your sleeve when your BLM decides to burst with Ancient Magic and then proceed to Divine Seal Cure 3 themselves. :D
Thief
For example, let's say you're partying with a RDM, WHM, THF, WAR, and BLM. You're all at level 30, and the THF wants to use SATA to help you gain hate and also to cause damage spikes, killing things faster and netting all of you more exp per hour. What you would do in this situation is let the WAR provoke first. You run around to the back of the mob, and the THF gets behind you. Make sure you're pretty close to the mob so the THF is still in range. Then, don't move and wait for the THF to use Sneak attack and Trick attack. The mob will turn and the damage spike will give YOU all of the hate generated by the attack. Let fly with Provoke, Cure 2, and tank as normal. Different jobs in the position of the WAR will function much the same way, though take care to be quick when a DRK is first voke. They have low defense and will get hurt quite a bit if left alone for too long.
Samurai
Samurai are skillchain masters and if you party with them often, you'll probably be expected to close the Skillchain. Paladins and Samurai are quite compatible for Skillchains..Actually, Samurai are pretty compatible with everyone. Moving on. Update: Samurai have been granted two new Job abilities, and are now beastly. They will give you a much harder time than before, but thankfully Samurai tend to not be retarded with their hate gain and will work with you. If all else fails, use Cover.
Dark Knight
Dark, moody, also answers to the name Batman. These guys are heavy hitters and if you party with them often, expect to be opening alot of Skillchains. I party with a Dark Knight three times a week in my static Party, and she and I have found some nice SC to take advantage of depending on what mobs we're fighting. Things to watch out for with this class is their Job Abilities. If they stack Last Resort and Soul Eater, expect to lose hate in the next few seconds. By the 40s most of them learn to watch their hate and won't pop all their damage enhancing JAs at once. Also by the 40s you've got enough tools to keep them alive and gain hate right back, so it shouldn't be too big a deal.
Dragoon
A knight with a lance in hand, and a cute blue Wyvern that flies around and dies alot. One way you can help with preventing the Wyvern death is by aiming the mobs away from the Wyvern. Lots of mobs use cone attacks, and making sure that they're facing away from your party members and their pets can help ensure that your Dragoon doesn't get a headache. Area of Effect attacks you can't do much about, unless you can interrupt them. Shield Bash helps with this, and picking up a Guardian Ring at some point may help you to interrupt enemies' attacks. Just macro it into your Shield Bash and go. Partying with Dragoons isn't much different from partying with anyone else, although you may find yourself closing skillchains this time around rather than opening them. Also take note about High jump and later on Super jump. High jump sheds a bit of hate from the Dragoon, allowing them a bit of leeway with their damage. Super jump, on the other hand, allows them to reset their hate. With a Thief and a Dragoon in the party, the Thief can SATA onto the Dragoon and the Dragoon erases their hate while you tank as normal. Fun, eh?
Monk
Ah, these guys. Potentially your worst nightmare for keeping hate later on in the game. Until then, they're a solid damage dealer and probably the most effective SATA partners for Thieves. After 40 you'll be opening up Fusion for them (Burst with Holy for extra laughs). There's not really much to say other than stay on your toes.
Blue Mage
I've only partied with 2 Blue mages so far, unfortunately. They can deal quite a bit of spike damage as well as pretty decent damage over time. Keep up on top of hate, and hopefully your Blue mage will be willing to work with you on hate management instead of being retarded and spamming spells nonstop.
Ranger
Can't believe I forgot these guys. Rangers, along with Monks have potential to be very annoying to keep hate from. Especially if they pull with Barrage. D: You might need to swap in a High Breath Mantle along with DD gear to make hate management easier. Otherwise, tank as normal and make full use of Spirits Within if you have it.
Bard
A party with a Bard is quite nice. Except when nobody listens, then the Bard develops an ulcer. When partying with a Bard, you'll most often have to run back to where the mages are sitting to get Ballad for MP. I personally prefer having acc/atk+ songs on, but it's not the tank's place to complain. MP regen is more important than striking your problems until they are no longer problems anymore.
Black mages
Delightfully squishy little powerhouses these are. The more intelligent ones you have nothing to worry about, they most often are quite adept at managing hate and won't intentionally overnuke and will even run behind you for Cover before casting a huge MB. The dumb ones will get themselves killed often. Don't worry about them, it's their own fault.
Warrior
Hate monster. That's it. A good Warrior can do incredible amounts of damage over time and have alot of potential for amazing spike damage as well. Most often they can time their WS to kill a mob outright and not pull hate off of you. Keep up with them and you'll have no trouble.
White/Red mage
Sorry to lump these two together, but they're quite similar in most regards. I run with both in a static party, and they compliment each other very well. Two things to remember: Most of the time, they know when you've got a status on you, because they've got logs set to show that information in their chat window. The other thing is to never demand Haste. If they can squeeze it into their cycle they will, and most likely if they're not casting it on you or someone else they're waiting for the timer to cool down. Patience is your best friend. As for Refresh, every Red mage at least learns how to make a functioning Refresh order for their parties. More often than not, you're at the top of it, so don't be an ass and demand it. Red mages are slaves only to their spell timers.
Summoner
To start, Summoners are not healers. They can do it, but that is not their main function. They can support the party with Blood pacts that cast various buffs, like Blink and Phalanx. They can participate in SCs with their avatars and are capable of MBing with their avatars as well. Overall a very versatile class, if somewhat underrated.
For the rest, you get to make your own conclusions. Every party combination can work with the right mix of skill and planning, and don't let anyone tell you otherwise. All that holds you back is the willingness of other players to try something new, if you can find a group that wants to experiment, then go for it. Having fun is the #1 reason to play. Good luck.
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Foods
This is delicious cake, Desu~ You must try it, Desu~
EDIT: Shallops is made of fail, stop using it. Accuracy and attack food is the way to go. Black Curry, Bream Sushi, Dorado Sushi, and probably Sole are better for you than any other defense related food. Also, at early levels you can replace Kabobs with Jack o lanterns if you really feel that you need moar accuracy. Use tacos when you really need that little boost to HP/MP, otherwise don't bother. Obligatory somepage link

Jack-o'-Lantern
Stacks: No
Duration: 180 mins
* Charisma -10
* Resist vs. Dark +25
* Accuracy +10
* Evasion +10
* Arcana Killer

Tavnazian Tacos
* HP +20
* MP +20
* Dexterity +4
* Vitality +6
* Agility +4
* Charisma +4
* HP Regeneration While Healing +1
* MP Regeneration While Healing +1
* Defense +25% (Cap: 150@600 Base Defense)

Bream Sushi
Stacks: 12
Duration: 30 mins

* Dexterity +6
* Vitality +5
* Resist Sleep
* Accuracy +16%
* Ranged Accuracy +16%

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Shields and you: A half-assed guide
Ok, so you've got yourself a skill called Shield Bash. Obviously, this class has an emphasis on the use of a sword and shield. There's a bit more to shield selection than just grabbing whatever's available and going with it though. Shields have 4 different sizes, and 4 different amounts of damage reduction/proc rate. Everything you've ever wanted to know about shields, complete with numbers that probably won't mean much to a casual gamer can be found here.
For those of us who aren't adept at skimming through data tables, here's a summarized version of that link.
Size 1 shields: low rate of damage reduced, higher proc rate than other shields.
Size 2 shields: more damage reduced than size 1, but lower proc rate.
Size 3 shields: higher rate of damage reduced, lower proc rate than smaller shields. This is the size of most shields after 30 that you'll be using, and for the most part are the better choice in terms of reducing damage you take.
Size 4 shields: Highest amount of damage shaved off, but lowest proc rate out of all shields. The difference between size 3 and size 4 isn't noticable as far as I'm aware, and in some cases may be a better choice than size 3. Shield choices should be situational anyway, just like other gears. Pick up a size 3 and a size 4 and see which works better for you.
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For now, this is the end. I'll be updating periodically, so be sure to check back. Special thanks to NeighborTaru for inspiring me to work this into a somewhat legible form.