In a computer RPG you have enemies to defeat and quests to complete. Both reward exp and allow your character to gain new skills and abilities. In a tabletop RPG you have a GM to fulfil the role of awarding experience.
This style of RPG is often quite different. There might be no one to reward your character so how does it make progress?
It depends upon what you wish to change about your character as to whether or not you could improve it but under most circumstances you will only improve by telling the story of how your character actually improves. Since you should be telling your character's story anyway this is not so difficult, providing you remember to portray what you yourself set out on your character sheet.
Improving a Skill
If you wish to improve a skill then you must work it into the story over time:
- Perhaps you write about your quest to find someone to train you
- Maybe you simply improve a skill between taking part in one story and the next
- Then again, if a story is open-ended and ongoing perhaps you improve a skill after a length of time taking part
It's fairly straightforward but don't improve too much at once or hand yourself an improvement just because you feel you can. You may have practiced at every opportunity but anyone can type "I practice, practice, practice" or "I find the zen master and he agrees to train me". Makes very boring reading and it's not exactly interesting to write either. On the other hand, you might write a great story in one or two posts, explaining how you got to become the only master chicken plucker in the land; however, if your story just sidelined the main plot and ignored other players turns you're avoiding character development in context of the thread so don't really deserve an improvement either. Just use common sense and if unsure, err on the side of caution or at least seek advice.
Adding an Advantage or Removing a Disadvantage
Let's imagine you wish to remove a disadvantage. First of all you need to have characterized that disadvantage. Over the course of a story you can attempt to have the character start to overcome this difficulty and eventually remove it. Telling the story of how you overcame a disadvantage is the only way of removing it.
You can also add an advantage to your character too but make sure you have a good reason, one that is story related and not just thrown in because you felt like it. The story of how you gained such an advantage must also be told.
Changing minor items can be done at your discretion as long as you are logically consistent with it. For example, you could feasably go out and buy a new sword but not if you're stuck in an empty field, miles from anywhere.
Found items are inserted into the story by the person controlling the plot, if the thread is controlled that is. They should try not to be too generous but reward characters appropriately. For example, you may wish your plot to contain a high amount of magic and magical items but bear in mind that you'll develop a player's character to only fit within the high magic genre and possibly exclude them from taking part (with the same character) in less magic intensive stories. Also bear in mind that without some form of restriction or logical foil, any items an NPC (non-player-character) drops the players will be able to pick up. You might not want that to happen or regret it later. Caution is therefore warranted.
If a plot is not being controlled by an individual then be sensible about adding beneficial items for yourself and each other. Don't just reward yourself with magic swords and the like just because it's too easy to type "I see a sword in a stone and tug on it only to discover I'm the true heir to the sword and, so the gaping knights tell me, the throne of England too!"
Pay attention to the style of the story too because you don't want to commit a faux pas by finding the flaming sword of doom when so far the story was geared toward gritty realism. On the other hand, if everyone has godswords then finding a dull and rusty dagger is hardly appropriate either.
If in doubt seek advice when improving your character
Also worth noting - in a controlled thread that thread's controller might offer a reward to a player for an outstanding story. Similarly, a moderator might reward a player. In both cases the preceding advice should be kept in mind too.