Kind of a dick thing to say. Am I not allowed to try to ensure I understand before hand so I'm not holding back a party by not being familiar with the game dynamics yet?
Oh, okay.
Offense
Flash: This is your AoE generation on pulls with multiple enemies. Popping a Flash at the beginning of a pull gets you some decent threat lead which ensures healers can't instantly pull off you. Using one between every rotation or two also helps a lot.
Fast Blade> Savage Blade> Rage of Halone: This is your single target emnity combo and really the only combo that matters for GLD/PLDs. Savage Blade does ok emnity generation but a combo'd RoH does a ton of emnity which makes the strategy of spreading out your combo to hold aggro on multiple targets viable. For example, once you've established threat on the primary target 1 with several rotations, on the next rotation use Rage of Halone on a second target. Next rotation can return to primary target and so on. The emnity gained from RoH will apply to a different target as long as its combo'd into.
Riot Blade, Shield Swipe: Situational skills, not usually worth the GCD you could use for more emnity generation.
Shield Bash: This is your on-GCD stun on a 2.5 second cooldown. Generally you can stun most casts those some special attacks will be obviously unable to be stunned. Enemies and players in this game can build up resists to repeated status effects in addition to diminishing returns. For example, your first stun will be 6 seconds, then the next will be less and less until it can no longer be stunned for n amount of seconds where it will reset and accept another full duration stun.
Shield Lob: I pretty much always use this to pull from range on single and multiple targets. It's also pretty decent for getting back enemies you lose aggro from but it does cost a lot of TP so if you can't get an enemy back in one or two lobs, it might be better to just walk up and do a melee combo. All that said this usually only sees use on the initial pull.
Circle of Scorn and Spirit Within: Both can be used as fillers in between Weaponskill GCDs while the latter can serve as an off-GCD silence on a 30 second cooldown. CoS does an initial hit before the DoT ticks so it breaks sleeping mobs.
Defense
Provoke: Has large range but generally want to save this for when you lose a target and you can't get it back. Instantly puts you above the target's current aggro +1 point of emnity so use a Shield Lob or a high emnity attack to re-establish the emnity lead.
Defensive Cooldowns: Just pop these when you need them, ideally in between Weaponskill GCDs. Awareness can usually be popped on really big pulls to ensure you take steady damage from all sources (versus random spike damage from criticals) which makes it easier on the healer.
Tempered Will and Cover: You won't find much use for these but they're handy in a few spots.
General Tank Stuff
Marking: Helps a lot early on to let your team know who to attack first, who to sleep, etc.
Macroing: Slapping a message macro on timed skills like Hallowed Ground can help your healer prepare for when to heal, or when you are silencing/provoking a target off someone.
Aggro Bar: Top left of your screen (by default) shows emnity the current target has relative to everyone else on the team. The numbers denote the order of highest to lowest aggro, with A having current Aggro.
Enemy List: Shows the general aggro of all your engaged enemies in relation to you. Goes from green (no aggro), yellow, orange, and red (you have aggro).
Single Target Rotation: Shield Lob, Combo with Circle of Scorns and Spirit Within in between when applicable.
Multiple Targets Rotation: Shield Lob, Flash, Circle of Scorn, Combo and CoS/SW in between, Flash after every couple of rotations while putting a Rage of Halone on the next target as primary gets close to dying.
Helping allies: Very important for melee DPS; don't rotate mobs around a ton as it makes it impossible for your melee DPS to get off their important abilities which rely on positional attacks. You can dodge an attack and move back to where you were tanking it once it's safe; this will ensure the enemy doesn't move around oto much.
Mobs with telegraphed moves: On certain moves by certain mobs, it's important to dodge or stun it if you can (like those with visible AoE cones and a lengthy cast time). Notable ones are Aiatar's Dragon Breath and Hydra's White Breath. Wyverns and dragons should generally be faced away from the party due to frontal cone AOE attacks.
Cross Class Abilities: Paladins don't have much essential skills to choose from, but nice picks are Stoneskin, Bloodbath, Foresight, and Mercy Stroke.
Attribute Points: VIT is the tank's primary stat.
Do you need anything else? Screenshots of my UI? Gear? I can reserve a spot on the Relic Primal train for you if you'd like as well.