I too DM very often, so I know what it's like to deal with complaining Players, to have to adjust or make a ruling on the spot, and how to squirm my way through a mistake I've made. I also know what it's like to deal with metagamers and rules lawyers.
As a result, I try to be helpful and to treat my PC as I treat my NPCs... as people other than myself. I make it clear to other Players that I'm role-playing a character and that what my PC does has nothing to do with what I may personally want. This has always worked well for me.
As a result, I don't argue with the DM right then and there on every single issue because it's a waste of time and energy... not to mention rude and a case, often-times, of second-guessing. For all I know, what appears to be a goblin may be a fire-spiting half- red dragon. I don't know what adjustments the DM may have made to keep the environment fresh and challenging any more than my Players know in my games. If I do have an issue with a ruling, I'll ask the DM after the game (without running around gossiping with other gamers in an attempt to "get them on my side") or I'll try to bring it up on the spot in a non-confrontary manner if it's that important (like my character or another character dying on the spot).
As a result, I try not to metagame. This is tough since I love monsters and know (like any DM should) the MM pretty well. There're few things worse than Players allowing their knowledge to interfere with how their PCs react. Hell, at the very least, they can be creative about it. You see something reptilian with big claws, horns, and teeth, chances are it's a dragon. Unless told otherwise, it's likely the dragon can breath something. Move away. My character had no idea it was a Behir although I did.