In the last year, I've started getting into Dungeons and Dragons with some friends. Overall, it's an enjoyable experience even before I started getting into it myself and there's something that always caused arguments; Roleplaying.
Let's start with the most basic roleplaying that there is in D&D, the Alignment chart.
As a beginner, I chose Neutral Good for mine as it seemed to offer a large degree of freedom and I'd pictured my character as 'good'. Neutral appears to be the least argued over because it allowed you to consider and justify your actions as you went.
I was surprised to learn that there's a lot of problems with Lawful characters. Some had chosen to interpret lawful as having their own code which they must never break, while others took the more traditional law enforcer route. While the first causes problems for the DM, and other players, if they weren't aware of it, the second often leads to in-fighting.
Consider a Paladin and a Rogue in the same party. The Paladin is charged with upholding the law, which he knows the Rogue has recently broken (pickpocketing, breaking and entering, general thievery) but reporting it could potentially lead to trouble for the party, a fight between the rogue and paladin, where the others would either need to sit out or take sides, derail the game if the DM decides legal action is appropriate and, most troubling of all, punishing the rogue for roleplaying.
Chaos doesn't need too much examination. They're notorious for doing idiotic things, desecrating graves, waking up dragons or paying a mage to transform a chicken into an elven prostitute. While there are technically three types of chaotics. Most of them can fall under the banner of 'Chaotic Stupid'.
However, there's more than just alignment that bother me about Roleplaying. Roleplaying a character requires that you've always got a caricature in your head of what you think that person would be like and you take the options that caricature would. Unless the choices are fairly well defined, you've just ruined the limitless possibilities that pen and paper RPG's have by limiting us to what 'what would ____ do?'. It can be a little better if you took the time to write a backstory and allow for the character to develop over time, but even that has a feel of railroading choices.
My advice for a beginner is don't roleplay, be yourself. That might seem contradictory to what RPG's represent but consider this; have you ever dreamed about going to Hogwarts? Thought about how you'd survive a zombie apocalypse? Treat the game as a chance to do exactly that. Play it as though it were real, as if these were your decisions to make. You are swinging that broadsword, you are sneaking your way through the enemy camp, you are reshaping reality with the power of your mind. Not only will this reduce the tension on you a bit, it'll reduce breakup of play; it's much easier to know what you would do in a situation then what someone else would do.