A big trap new tanks make is using cooldowns reactively instead of proactively. Most tank classes have an ability that reduces damage by 50%. New tanks consider cooldowns as “oh XXXX” buttons. Don’t fall for this trap.
Let’s do some napkin math.
You’re at 100% health. You take a big hit and now are at 20% health so you press your big cooldown and effectively have 40% health before you die. 50% damage reduction and only 20% health so it takes damage equal to 40% of your health before you die. You used it reactively.
Now let’s look at it proactively. You’re at 100% health and use the cooldown. You take the big hit but at 50% damage reduction you’re still at 60% health and you require 120% of your health to die while the cooldown is still up.
Use cooldowns proactively so you can survive. Your healers’ mana will last longer and they won’t have to cover for you.
When you make the transition from being a raider to assuming the role of raid leader or just wanting to be a better raider there comes a macro “big window” view you have to take into account.
As a raider you only care about your damaging/healing/tanking abilities and how they interact with the raid. Always running the recount/skada/combat parsers and where you’re at on the meters. As a raid leader you have to take a macro “big window” view towards the raid as a whole.
Double potting (using one potion pre-pull and then another during combat) is a good habit to get into even on farm night. Kill the boss faster and move onto the next boss faster. Now take that and multiply it by 20+ people because as a raid leader you now have to view it at a macro level.
Cheap enchants/gems/flasks are another trap. The blue 630 item level piece isn’t “worth a good enchant,” but on a macro level it’s the best gear you have and if everyone thinks cheap is okay because the gear isn’t worth it then on a macro level you have an issue. Now take all those missed stats and multiply it by the number of raiders. The math starts to add up.
On a macro level you want to kill or practice on as many bosses as you can during your allotted raid time. Allowing single or no potions and cheap or no enchants/gems/flasks isn’t helping towards your goal.
Be a good raider/raid leader: Think macro, not micro.