These are my responses to the Monsters and Manuals blog article about things that Game Masters tend not to talk about.
Book binding. Not sure how well my Drive Thru RPG books will stand up to the test of time but at least one doesn't seem to have enough space between the covers. The covers are always bursting open as though too many pages were shoved in unless weighed down. The Pathfinder core rule book also shows the downside of the decision to combine Player and GM material. Its bursting at the seams and part of the spine has torn loose because it's so big and heavy. I don't think this is due to cheap binding but more due to the nature of the beast.
"Doing a voice". I'm terrible at accents and most of my players react poorly to accents as well - from me or each other. We do try to change it up a bit through tone of voice and word choice, though.
Breaks. My game has no pre-determined breaks. People go to the toilet when they feel the need.
Description. Tends to be quite tight with a few telling details where necessary. I sometimes have trouble with description in combats as my players are more visual than I am and are better at keeping track of where people have moved. This can be annoying when I think they're elsewhere.
Where do you strike the balance between "doing what your character would do" and "acting like a dickhead"? Is it likely to hamper anyone's enjoyment? If not, go for it. I know I can find it hard to avoid doing what my character would do, however. Sometimes its hard to judge if it's annoying someone else.
PC-on-PC violence. Not allowed in Dystopic unless very special circumstances permit it and then only with my permission / overwatch. More flexibility in Flashpoint though even there it's based more between Lhye and Proteus who are big boys and manage to keep it all at a reasonable level. No serious PVP would be allowed in that game. I have run a Vampire LARP, though, and PVP obviously worked out there. It all depends on the type of game you're running and whether it can withstand the player characters attacking each other and the resultant paranoia / vendettas that can ultimately ensue.
How do you explain what a role playing game is to a stranger who is also a non-player? Cooperative storytelling / improvisational theatre using games of chance (dice) to see if something succeeds or doesn't.
Alchohol at the table? No.
What's acceptable to do to a PC whose player is absent from the session? In Flashpoint I ignore them. In Dystopic, they just happen to need to leave for a session. I've tried other options but they just haven't worked for me. I've never killed a PC whose player was absent. Just doesn't seem right.