Hey that is a-okay!
I come prepared with visuals.
Let’s say this is my 5 man team. Yes, we’re fortunate enough to have a Holy paladin tank. We’ll say for demonstration purposes that I am the tank.
In this visual, my target is Kaltari, but we’ll say it’s a mob. Your job as a DPS is to target what I am targeting and focus it down quickly. You should do yourself a favor and set up a targeting keybind or you could also use the tab target feature. Usually a /focus macro will work just fine if you need the added bonus of always seeing what the tank wants you to hurt.
Sometimes the tank will also be kind enough to put a marker over the item that they want killed. Those will look like:
This booty game is strong and needs to be DPS’d down. (Please don’t actually kill me. I’m a tender young flower.)
Use these visual guides along with DBM to understand what your tank is asking of you. Focus targetting is also a big thing in PvP, assuming you’ll ever get into it.
Just do yourself a favor and don’t listen to shitty DPS. There are going to be people who just want to gear blast things and that doesn’t always work. Some instances and raids still require you to do mechanics or you will die. Listen to your tank, follow their cues. Let the idiot DPS die who feels the need to tunnel without listening to directions or following their tank.
The only time I’m going to say that this information may not be helpful is if you have a really bad tank. And when I say really bad tank, I mean my dead grandparents could hold a dragon better than them, so with that in mind, go forth and conquer!
EDIT:
I feel the need to add this as well.
AVOID TUNNEL VISION. I’m sure at some point in your life you’ve experienced a thing called tunnel vision. If you haven’t, I’ll explain anyway. When you focus so hard on something and you’re caught up in the moment, your peripheral vision can sometimes be clouded or the information can be missed.
IT IS REALLY EASY TO DO ON BOSS FIGHTS. YOU NEED TO AVOID THE TEMPTATION TO DO THAT. That is what wipes raids. Your focus on the boss is one thing, but focusing and following directions is what keeps you alive, kills trash and gets the boss down quicker.
Not going to lie, as a tank I have been known to ignore pulling mobs off of DPS that are ‘problematic’ (AKA: they keep pulling things that don’t need to be pulled) especially in content that I outgear.