Most people will read this going, "yea I know all of this what's your point?" To be honest, I see so many people neglect or refuse to do these simple things in group content. Here's a list of some basic skills you should learn before stepping into group content:
1. Blocking: Block is your friend. A lot of people apply logic into what they can and cannot block, but ESO doesn't usually follow any real sound logic. Blocking mitigates a lot of damage from dungeon mechanics, and even as a DPS can save your life. Blocking in some cases is easier and better than roll dodging, but you should pay attention to when this is used.
2. Red circles and why they are sometimes good and bad: Obviously you see a red circle, your first thought should be don't stand in it. 8/10 times, you're right. Watch your feet, for the love of god. But as I said in blocking, sometimes a mechanic requires you to switch up the rules.
3. Interrupt: I cannot tell you how many people don't know or do this. Trials have so many adds/bosses that require you to quickly react and interrupt. In order to interrupt, you need to bash a target. Bashing by default is left and right mouse buttons at the same time. I thought this was stupid, and rebound it to F, and moved my interact with player to V. You may want to do the same. You interrupt when an enemy has red sparks coming out of them. Having active combat tips is pretty important if you're still learning. Combat cues is what shows the red sparks.
4. Don't panic: People usually take a significant amount of damage in trials. Don't worry, keep calm and DPS on.
5. Synergies: Use of synergies (Throwing and activating) is insanely important. You trigger the undaunted passive, and restore resources for the entire group. Tanks/Healers running things like Alkosh and Twilight Remedy benefit from synergies. Use them, unless a mechanic forces you not to.
6. Self sustain/shields: Healers aren't your personal bitch. Having your own type of sustain or shields is insanely important. For Stamina, the basic universal heal is Vigor (assault tree) and for mages it would be annulment (light armor tree).
7. Focus rezzes when people die: Unless a tank is assigned to revive, DPSs should be always aware when people die, where they died, and when a good time is to pick them up. Tunneling into a DPS rotation and leaving your teammates dead hurts DPS overall, so take a few seconds, revive the dead, and continue onwards. It is not the job of healers to do so, they're busy keeping your lazy ass alive.
8. Don't back pedal: If something is beating your face, stand there, shield up and wait for a tank or healer to help you. If you have aggro, walk to the tank, and they will take whatever is on you back to them. If you back pedal, keep going, till you're out of the trial.
9. Don't excessively talk in coms: I don't need a Madden play by play on how you died, cause I don't care. Tanks and healers should be the only ones talking, unless a mechanic requires more communication.
10. Know who to focus: Almost every pull, including trash pulls, there's a priority target. If you don't know which it is, either listen up, or ask. If certain adds don't die right away it can wipe groups, or give us a really hard time.
These basic player mechanics should be learned, to the point its muscle memory. I promise, it'll make you a great player in the long run. You'll die less, your DPS will climb, and you'll become far more useful.