But at the end of the day I think it is really introductory level stuff, which shouldn't (but all to often does) need to be said. It isn't the only good advice out there on the topic. Look, Robot's article on 11 ways to be a better roleplayer, goes a little more in depth, and contains what I guess could be called the two most important intermediate level skills when it comes to role-playing, I.e. "do stuff" and "don't deny."
What I thought might be interesting, is looking at the layer of advice just above that.
Work with the story:
When you sit down to make a characters, it is worth talking to your fellow players and GM. This isn't just so you can find out if anyone is playing a cleric yet.No, this is an opportunity to make decision about who your character will be, and how that will reflect and/or compliment the theme and mood of the game's fiction.
It is all well and good playing Paul Pleasant , Paladin of Palor in his Pristine Plate, but if your GM has pulled together a Ravenloft game of dilettante investigators, hot on the trail of a serial killer, Sir Pleasant is going to be a little off key. Take the time to really get to grips with what the campaign is going to be about, and find ways to play of that.
Agree on a social contract: So in 11 ways to be a better roleplayer, their are a couple of a fairly explicit instruction; This is great advice, to this day, I am more than a little bitter about having one of my characters and "Fisk'ed with a car boot, by another PC. That was the height of fun, let me tell you.
However that advice isn't the whole story. There are games where inter-player antagonism is part of the deal, and a lot of fun to boot. Many horror games are all about making the players uncomfortable. The secret is to have everybody on the same page, and to have consented to the material in play.
You see, if wasn't that I object in principle to one of my characters having been decapitated by another players character. Rather, it was that I was working under the implicit assumption that we were on the same side, and would not do such a thing to each other. Knowing that was the game were playing, would have changed the way I approached the game.
Equally, when I sit down to run Call of Cthulhu, I am setting out to make my players uncomfortable. It is for both myself and my players, a big part of the fun of the game. However, I have their permission to take them to that place, and that, combined with my agreement not to touch on certain subjects, frees them to trust me.
So talk with your GM and you fellow players, has out rules as to what is and isn't acceptable at the table. This can be a useful place to cover other things, like those pesky personal hygiene issues which still occasionally plague out hobby, and use of tablets and phones at the table.
Use all your senses:
Two of the best bits of advice Lex gives in his podcast are ask questions and contribute to the fiction. Well I heartily support this advice but would add, use all your senses. Ask what a place smells like, ask about the birdsong that can be heard in the NPCs garden, and describe the taste of the walnut bread at the tavern.
Set yourself goals:
If your character wants things, and will actively pursue them, that is another thing for your GM to grab hold of. It can be a way to steer your character towards plot or a meaningful rewards for success. Most importantly, it helps to make your character more rounded and believable.
Set yourself rules:
An often under-appreciated tool of creativity is working within constraints. Being unable to do the first thing that pops into our heads, forces us out of our comfort zone. It makes us find new and interesting ways to approach a problem. By applying stict rules to our characters, we can create characters much further outside our norm.
Such rules can be things like, "this character never says no to anything", "will not kill another human under any circumstances" or "this character will not willingly be the target of a spell." Next time you play a new character, try taking on such a rule, and see where it takes you.
However, if you take this approach, remember not to deny another players actions(unless you've agreed that is okay ahead of time). If the rule stands to act as a block to the ongoing adventure. Make you response proactive. The answer shouldn't be "my character wouldn't do x" it should be "my character wouldn't do X, but he would do Y, which should get him to the same position.
People aren't 100% consistent. The greatest philanthropists in the world have examined prejudices, and even the most cynically criminals have friends. Heroes can have phobias, and villains can act in the common good. When we make characters who are 100% consistent, what we get, is not a realistic character, but a stereotype. Consider ways in which your character acts outside of what might be expected of him.
Make poor choices:
This is a big one, with effects on various parts of the game, it also acts as the next step on from embracing failure.
The realisation that failure is okay, is a big deal. It allows us to see what else failure might be. Just look at Indiana Jones and the Raiders of the Lost Ark.
Indy's failure to judge the weight properly leads is the trigger for action, as previously established threats are all brought into a new context by the collapse.
Clealy for the viewer, Indy's failure is a good thing. Failure by our characters can be a good thing for us the player too. The prime example of this being the escape of a recurring villain. At this point, I hope we can agree that failure can be a good thing. Before continuing lets take about decision making.
Then there is the fact that people, as a rule, aren't very good at making good decisions, and there are a lot of things that make them worse at it. This is especially true when it comes to making decisions about things we do not understand well. When I say well, I mean things we can and have applied the scientific method too. As a result, your average PC in an RPG is usually ill equipped to good decisions about such vague and abstract things as say, which feats they are taking.
All this combines to mean that making poor decisions at the table CAN lead to more interesting and believable characters, especially when mechanical choices lead to more generalised and rounded characters, or behavioural choices reflect motivations other than success.
Don't be afraid to say, it does not matter that this is the optimal choice, because the other option is cooler.