All elitism and epeen aside, I've been astonished the past few days in seeing people joining my group totally ill-prepared to take on the task at hand. Ignorance of your role is one thing (ahem, PL), but when you combine that with the likes of a Lv38ish Gladiator in full DoH equips without a shield, I mean, c'mon.
Know Your Role. I won't assume that everyone that begins playing FFXIV has played at least 10 MMO titles before it. Though the party mechanics have been somewhat blurred as to the classic roles of tank, melee and healers, this traditional setup is still most effective.
-Gladiator is meant to tank and lead the party from enemy to enemy while spamming defensive and enmity generating abilities. If you don't want to be busy as hell trying to hold the attention of every attacking mob away from the rest of the party, then go for one of the other DoW as a main. It is probably the only class where you truly are at your best when spamming everything you have available in the way of the aforementioned abilities. As healing yourself is one of the best ways to retain enmity, use Stygian over Shock Spikes and employ Siphon MP. Remember, Area of Effect is your friend! Your gear should prioritize DEF>VIT>EVA.
-Thaumaturge works best as a nuker, debuffer and support healer. Always be mindful of enmity when casting spells, as if you are in the orange then your next AoE nuke will most likely send the lot of them hurtling toward you. After that, you will no doubt spam yourself with your best healing abilities, further adding to the problem. Your gear should prioritize INT>MND>PIE.
-Conjurer is the optimal choice for a healing role. Many of the same cautions that are inherent to Thaumaturge also hold true with Conjurer. The only divide lies in the fact that a THM truly can mitigate its enmity as opposed to the necessity you have in keeping everyone's HP in the white. You should always think twice before touching Curaga and especially Curaga II, as these are almost guaranteed to pull hate from at least one mob if not all of them. Remember, Stoneskin is your friend! The best you can hope for is a competent party and a decent tank. Your gear should prioritize MND>INT>PIE.
-Disciples of War are generally more relaxed and straight-forward in contrast to the previous three classes. Now that the likes of Raging Strike and Ferocity don't equate the enmity of Provoke and Taunt respectively, you are able to fully buff that next Victimize or Doomspike with less consequence. A melee's second biggest responsibility is to stay out of the way of incoming damage; That means paying attention and situating yourself behind or beside the mob, depending on its AoE capabilities. Because you will occasionally draw hate either from damage output or aggro, make it a habit to stick Foresight and Featherfoot on your bar; That's virtually two attacks negated with little recourse in enmity generation. It is also a good rule of thumb to save a spot on your bar for Raise/Resurrect - it does come in handy in emergencies. Your gear, arguable by circumstance, should prioritize ACC>STR>DEX.
Come Prepared and Equipped. Hopefully your party leader is intent on leading you all to a worthwhile experience wrought with danger, suspense, excitement and DEATH. And because we all know anything worthwhile isn't easy, don't expect that Coatee set you threw on through your last PowerLevel marathon to cut it. Although video games are in general an utter waste of time in their own right, do yourself and everyone else a favor and check beforehand that your gear is decent, in good repair and that you have plenty of arrows to suffice the duration so that time isn't unnecessarily spent on things that could have been prevented.
Mind Your Manners. I don't (shouldn't) have to remind you all to say please and thank you when it's warranted, as this section is more about ingame courtesies, rather. Don't criticise another player or situation in any channel outside of /tell. Even then, make sure it's much more constructive than patronising. Don't join an event with less than an hour to spend doing it, emergencies notwithstanding. When on a venture that is far away from your Home Point, be a good sport and set your HP at an Aetheryte nearby; If your party leader is proper they'll put the party together for you, teleport you to camp and back again! And the list goes on..