So I quite enjoyed this article at I Blame the Dice!
I have some experience with online play and Play-by-Posts. I actually ran one (rather poorly, looking back) on the Paizo forums that lasted for roughly a year, and another that lasted only a few months.
If you’re playing Pathfinder or D&D I really recommend looking at their specific forums for playing online. There’s a great community of players on both sites that will jump on the chance to play - granted, this means you will likely have to GM, which is a huge challenge. You can always throw up an application and apply to other games as well over there.
As for making yourself a Role-Player instead of a “Roll-Player”, I always do a few specific things, and keep in mind, because I’m a “Right Brained” so I tend towards this anyway.
- Know the Campaign Setting. Read it, love it, and accept that your GM is going to change it and that your character will grow with it. I say this because if you don’t know the world, how can you interact with it? You have to know who the people in your town are, the king and queen and political figures, the tenants of the faith of your culture, etc. If you don’t know that, how can you immerse yourself in the game world? That being said, your character doesn’t have the knowledge you do - maybe he’s a country bumpkin, or she’s young or still in school. Keep this in mind. You may know that Vol is the scion of The House of Death, but your character likely has no clue.
- Embrace that one shit stat you have and roll with it. Low Charisma score? That doesn’t mean your character has low self esteem. Low strength? Maybe they want to be strong and will grow in strength as they progress in the story. You don’t always have to make the "right choices" when your level up. Make the best choices for their development. Shape your character to tell the story rather than be perfect. Play with strengths and weaknesses, and love them. The best characters have both.
- Be a team player. I say this because a lot of times, people who power game or “Roll Play” forget that they don’t have to be the best at everything because they’re part of a team that work together. Never forget that you’re a piece of a greater whole, and that you should have a specific role to play. You’ll be the best at something - but you someone will be better at something than you are - and that’s a good thing. When it’s there time to shine, let them have the spot-light. The story is about The Fellowship, not just Frodo.
- Draw your character. Have a visual representation of your character to show your group, and for you to look at when playing. This helps me remember that my character isn’t just a chaotic cluster of numbers on a couple sheets of paper, but is a real character, complete with their own hopes, dreams, and ambitions. Can’t draw? Commission it, ask for help, trace, or rip and image from a book. It’s really about having something that allows you to say, “Yeah, this is me.”
So that’s my advice on how to “Role-Play” vs. “Roll-Play”. Have some input on the matter? Don’t be afraid to submit it!
- Know your character’s stats and stories. Know what you can do, and what event in your character’s life gave them these abilities. They had to learn it from somewhere. How? Where? Why?
Roll some 20s!
Though the original question was about play-by-post, a great response for how to develop characters in a tabletop setting!