The general idea of tanking is easy. Mostly you can just use your enmity combo on PLD once in Shield Oath during raid, and have a ninja shadewalker you on pull. This will make it so you should never have to worry about aggro, but this also doesn't mean to not keep an eye on the enmity bars. You can mostly relax though and use your DPS combos from there on.

As Spartan said, Communication and knowing the fight is critical. You need to know that if you stance swap, when is it appropriate to swap back in the instance of add phases or big damage going out. Communication with your team is needed, but you need to make sure out of all else that your co-tank and you are on the same page as to when and how to conduct swaps. When it comes to swapping now, pay attention to the other tank and the aggro bar for the both of you. If you're tanking and they provoke off of you and take aggro, you cast shirk on them to give them more aggro so they also can DPS more. Generally its to prevent them from having to use their enmity combo over their DPS.

When it comes to how you use your stances, as in, whether you like to use Sword Oath on MT or stick to shield oath, that is mostly on you and how comfortable you are with the fight. If you can accurately assess the damage you will take when popping certain cooldowns, and the healers are prepared for that as well because they know ahead of time you'll be using sword oath, then you're good to try Sword Oath tanking. No one will mind if you stay in Shield Oath to be safe when MT. (of course just make sure you turn that off when swapping) Also when OT, obviously make sure to use Intervention on your MT during tank busters. Your gauge as OT isn't used for much else.