Thunder only happens when it's rainin'.
Players only love you when they're playin'.
--Fleetwood Mac, "Rumors"
Someone with a writing style markedly similar to mine has been writing posts on reddit, and by pure coincidence, I've not had much of a chance to write here. But a question there--what advice is there on being a better player?--caught my eye, so I thought I'd write up a few observations of my own.
Like many simple questions, this one hides a lot of complexity behind it. Being a good player means at least two things: first, it means making good decisions for your character; second, it means being a good member of your gaming group. The two reinforce each other, but are not the same. A third meaning--how to dramatize your character--is mostly orthogonal to these, so I'll skip over that for now.
On the most basic level, making good decisions for your character involves two steps--first, gather as much information about your surroundings as possible, and second, think about your options and select a good one. When I say "gather information", I'm not talking about rolling the Gather Information skill, or anything that requires a dice roll or any movement by your character. Instead, I'm talking about visualizing what you've been told, and asking questions of the GM for anything that you personally, as a player, don't have a grasp of.
Visualizing: It's pretty basic, and most people don't have a real problem with it, but it never hurts to take it a bit further. The simplest advice I can give about visualization is to close your eyes for just a few seconds and mentally plant yourself in the space your character occupies. If you're exploring a throne room, for example, visualize the throne, sure, but realize you're probably looking up at it, not down (unless you've climbed a wall or are flying somehow). Think of where your fellow adventurers are: to your left, to your right, in front of or behind you? How far away are they? How far away are any NPCs? Mentally triangulate and connect the critical elements of your immediate location.
Asking Questions: Mostly, this is to ensure that everything your GM thinks you know, you know. The first 3 of the journalist's 5 Ws--Who, What, Where--are the most likely candidates for questions. Engage your senses and ask what color is the magic wand, does the air feel cool or warm, are there any funky smells, and do you hear anything unusual. Be quantitative, at least approximately. Ask how big the stone doors are, or roughly how many people are in the market square.
(A good practice to accompany this is to let the GM know why you're asking. Don't just say, "How deep is the pit?" Say: "How deep does the pit look? Because I'm thinking of jumping it, but not if it looks like missing the edge will kill me.")
After that, selecting a good option is highly situation-specific. The only advice I'd have for that is to think ahead while the GM is resolving actions with another player. Pay a little attention to what happens with them, but keep an eye on what you want to do next.
As far as being a member of your gaming group is concerned, it can be mostly summarized as: be an adult. Don't pout when things don't go the way you planned. Ask for advice, offer help, and don't interrupt when others are talking. Don't check your phone messages. Don't play other games when your character isn't in the spotlight. Don't bring in any electronics you don't need, unless you have the game rules on a pdf or maybe your game's SRD, if they have one. Be someone that people like to be around.
But for RPG-specific advice, I'd add: know your character sheet. Know the rules that pertain to what you have written down there. Know the difference between acting dramatically and hogging the limelight. Remember that characters may have lots of conflicts, but players should have few. Be prepared for your turn, when it comes.
And lastly, ask yourself the question, why am I playing this game? That's not a deep philosophical question, although you could certainly follow it up with one. But I really just mean, what kinds of things do I want to happen in the game? RPGs do not have a single goal, so you have to come up with them on your own. Ask yourself: Do I want to show off my acting chops? My problem-solving skills? Do I want to imagine dragons and castles, or do I just like getting out of my own skin for a while? Knowing your own motivation is the best way to gauge whether or not the game is meeting them, and the first step in ensuring that it does.