One of the things that you are going to have to grapple with when you visit a card room is the etiquette of the actual room. Card room etiquette is a bit difficult to conceptually know about and that is why there are a lot of things that people need to know. While most of these situations are not likely to come up anytime soon in your card room, knowing what the rules are might help you very much. Just as a final note, these card room rules are not universal, but rather are modal; the ones that are most likely to be in place in your card room just from natural statistics. The actual rules in your card room might differ.
Adjudication: When the house adjudicates a decision, it starts with the dealer. When two players get into a fight, then the responsibility falls to the dealer in order to adjudicate the fight and hand down a decision. However, if the dealer can not do that, then they will call over the floor official that is closest to them and get the official to adjudicate. The official will come up with a decision and you will usually find out that the house ruling is final. There has to be someone there to keep order and if you do not like the house decision, then tough luck.
Intimidation: Because of the recent boom in poker, many bullies have started to try and get their opponents to either fold hands or not raise/bet by intimidating them physically. Intimidation is something that most officials take very seriously and as such it is something that there is a zero tolerance policy for in most casinos. Therefore, intimidation is punishable by removal from the game, temporary time-outs or even ejection from the casino or card room if things get really bad. Intimidation can consist of a number of things including physically standing up and over your opponent or even just standing up at all. Try not to practice it, but if part of your game is intimidation, make sure you find a casino that allows it before you get yourself into an embarrassing situation.
Showdowns: When there are two players that are left in the hand (or more than two players), the person that made the initial bet that was called is the one that shows their hand first. So if a person bets $20 and another person raises to $40, the person that raised to $40 would show their cards first if the first person called, because they made the initial bet that was called. If a person does not have a hand that beats the highest hand shown at the moment, they have the option of mucking their cards face down without ever showing their hand.