Noisms has it exactly right. Most problems with gaming can be boiled down to people just flat out being jerks during what's supposed to be fun.
In that light, I present below advice from the DM himself from B1, advice that everybody should be intimately familiar with before they're allowed to open a book, no matter if that book is a glossy PHB from WOTC or a dingy and well-worn little brown book.
TIPS FOR PLAYERS
Beginning players would do well to profit from some basic
advice before beginning their D&D careers, and with that in
mind, the following points are offered for consideration:
1) Be an organized player. Keep accurate records on your
character (experience, abilities, items possessed, etc.) for
your own purposes and to aid the Dungeon Master.
2) Always keep in mind that the Dungeon Master is the
moderator of the game, and as such, deserves the continued
cooperation, consideration and respect of all the
players. If you disagree with him or her, present your viewpoint
with deference to the DM's position as game judge, but
be prepared to accept his or her decision as final—after all,
keep in mind that you may not know all aspects of the overall
game situation, and in that case, not everything will always
go your way!
3) Cooperate with your fellow players and work together
when adventuring. Remember that on any foray into the dungeon
or wilderness, a mix of character classes will be beneficial,
since the special abilities of the various characters will
complement each other and add to the overall effectiveness
of the party.
4) Be neither too hasty nor too sluggish when adventuring. If
you are too fast in your exploration, you may recklessly endanger
yourself and your fellow adventurers and fall prone
to every trick and trap you encounter. If you are too slow, you
will waste valuable time and may be waylaid by more than
your share of wandering monsters without accomplishing
anything. As you gain playing experience you will learn the
proper pace, but rely on your DM for guidance.
5) Avoid arguing. While disagreements about a course of
action will certainly arise from time to time, players should
quickly discuss their options and reach a consensus in order
to proceed. Bickering in the dungeon will only create noise
which may well attract wandering monsters. Above all, remember
that this is just a game and a little consideration will
go far toward avoiding any hard feelings . . .
6) Be on your guard. Don't be overly cautious, but be advised
that some non-player characters may try to hoodwink
you, players may doublecross you, and while adventuring,
tricks and traps await the unwary. Of course, you won't avoid
every such pitfall (dealing with the uncertainties is part of the
fun and challenge of the game), but don't be surprised if
everything is not always as It seems.
7) Treat any retainers or NPCs fairly. If you reward them generously
and do not expose them to great risks of life and limb
that your own character would not face, then you can expect
a continuing loyalty (although there may be exceptions,
8) Know your limits. Your party may not be a match for every
monster you encounter, and occasionally it pays to know
when and how to run away form danger. Likewise, a dungeon
adventure may have to be cut short if your party suffers
great adversity and/or depleted strength. Many times it will
take more than one adventure to accomplish certain goals,
and it will thus be necessary to come back out of a dungeon
to heal wounds, restore magical abilities and spells, and reinforce
a party's strength.
9) Use your head. Many of the characters' goals in the game
can be accomplished through the strength of arms or magic.
Others, however, demand common sense and shrewd
judgment as well as logical deduction. The most successful
players are those who can effectively use both aspects of the
game to advantage.
10) The fun of a D&D game comes in playing your character's
role. Take on your character's persona and immerse
yourself in the game setting, enjoying the fantasy element
and the interaction with your fellow players and the Dungeon
In the words of Bill and Ted: "Be excellent to each other."