Do!/Don't! Keep the game fun.

Nice collection of advice. There are few more things new players don't know (will send PM)
And there is also this:

I appreciate it. I'm new to MP and still learning the builds and the etiquette and all that jazz.

I am always happy to hear that ^^ As for etiquette if I would add those to the list it would become much longer I just wanted to focus here on things which are annoying and sometimes making players upset mostly because of "well coded" stuff  (e.g. if you do not know this bug why should you not shoot at the dragon when it flys around at low health? ^^)

Thank you HunterKipling for adding the specific agents who cause the problem with the mines I change that in my first Post.

No, better to crawl into the middle of the dragonfire that just downed you.

And the most important of all...

 A wise advise from the Beagle. 

Evil! (Write it down in my to-do list silently. )

Lol
Some gold here

For bigger maps like Ferelden Castle, if you end up in the fade halfway through a level it can be tempting to exit and rejoin rather than float around and wait. Which is fine. UNLESS YOU ARE THE HOST OF THE LOBBY. If you do this as host, host migration happens and everyone in the party has to start the level again from scratch.

Sadly, I know this from personal experience.

Conversely, if you are host and a level bugs and you can't complete it, then DO exit. The others will have to restart the level but at least they won't lose all of the progress and experience they earned to that point. If you see a bunch of players jumping up and down in front of you, there is a good chance they are trying to tell you something.