Having played and run tabletop games for over 8 years, I’ve learned a lot about what it takes to create a fun, interesting, and engaging character in almost any tabletop RPG. While the strict definition of those first two descriptors means there’s a lot of subjectivity involved in the process, there are a few things you can keep in mind while you figure out what you think would be fun and interesting that would help keep the game an enjoyable experience for you and those playing with you. For the most part, they fall into two categories I’d summarize as “the ability to be engaged in or by the story and other characters” and “a series of imperfections that expose them to risk.” These are two fundamental parts of creating a character that are generally built into tabletop games with a basis in hard numbers but they can often be overlooked in other games. Additionally, the later can be avoided in hard number games like Dungeons and Dragons if the player optimizes their character in such a way that obviates all risk.
For the most part, exposing your character to risk is part and parcel with playing a tabletop game. There are some characters who avoid most risks as a result of their playing making them cowardly or extremely self-centered, but those often include the risk of negative social consequences or a loss of advancement opportunities (advancing via level or ability progression, specifically). Risk is a pretty broadly defined word and the only real way to avoid it entirely is to find a way to make your character so powerful that nothing bad can happen to him or to play with a group of people who are going to enable your (the player’s) machinations and rule-lawyering (a term that means you rely on your knowledge of the rules, their exploits, and the various gaps between them in order to manipulate an interaction in the game, either as the player or as the character, so that it resolves to your advantage). Typically, the only players who do this are the ones who actually enjoy having a character who never fails, so most of the failure here is the fact that it often frustrates other players, by either wasting their time as you argue through some obscure rule with the GM (who is always the final arbiter of rules but often lets things slide just to get the game going again) or by making their characters essentially useless.
Risk is essential because it the main vehicle for growth and change in the story your character is telling. Even if they aren’t a central part of whatever plot is currently unfolding, being unable to make them strive or risk something means they’re going to remain unaffected by whatever happens. They might learn new information or they might gain interesting new abilities, but there’s no way for them to actually change their course unless they fail something. Failure is the best teacher there is and sometimes the price of the lessons we learn are steeper than we’d like. If there was no risk of failure or loss, then what is the point in playing out the scenario? We all roll dice because we’re not certain of the outcomes and removing the chance of failure removes the need to roll dice. At that point, you might as well be reading a book or listening to someone tell a story. Sometimes, you lose it all and your character dies. Sometimes they lose something important to them. That’s just part of the game and the sooner you accept that you might need to let go of a character you loved, the sooner you’ll be able to really enjoy the character you’ve created and their experiences in the world of the game.
Thanks to the structure of games like Dungeons and Dragons, your character is automatically a participant in the story that’s about to unfold. If your character wouldn’t actually leave their humble origins and go on an adventure, you don’t actually make them. There’s always some part of them that has a goal to accomplish or some reason to want to explore the world beyond their village. In other games, it isn’t always that simple. Some games, like any that use the Fate system, require a little more intervention on the player or GM’s part. A lot of the Fate system games are based a little more in real-world sensibilities. For instance, the Fate game I’m currently playing in is based in a fictionalized version of the city we all live in because we’re familiar with it and the game requires a certain amount of city knowledge in order to navigate the game and tell a story together (the Fate system is much more role-play intensive and gives more story-telling power directly to the players). As a result of this more real-world feel for our game, are people need to be functional adults in this game. We all have lives and jobs and responsibilities that existed before the game began and most of which still exist after the game has begun. If you weren’t careful, it would be possible to create a character who has little connection to the plot and the other characters, which makes it even more difficult to keep them involved in the story. The GM can only do so much. The rest is on the player to write their character in such a way that it is easy to involve them in the story or else they’ll spend more time sitting out than anyone else.
The easiest way to get your character involved in the story is build in some flaw that allows the GM or other characters to pull them along. Maybe they have really bad luck and a history of being in the wrong place at the wrong time, as my character in the Fate game does. Maybe they’re an insatiable thrill-seeker with little regard for their personal safety or the lives of others, like my first fifth-edition character was. Maybe they feel it is their duty to protect the overlooked members of society and are banished from their home for speaking out against their lord when the lord raised taxes too high for the peasants to afford. Maybe they’re easily swayed or they have debts they need to pay. Maybe they’re morbidly fascinated by crime scenes and bought a police scanner so they can go gawk every day. Maybe they are so meticulous that they can’t rest until they’ve reviewed every little detail that seems out of place. All of these things have one thing in common: there’s something that allows them to be easily put in danger, manipulated, or otherwise involved in whatever is going on at the time. If you’re having trouble thinking of something that would be applicable to your current game, just ask the GM for suggestions that would make it easier for them to set a plot hook or get the players involved in some story they’ve cooked up.
How you specifically apply these ideas is really up to your own interpretation. Like I said earlier, your definition of “fun” and “interesting” is probably different from my own and you should make sure your character fits into them. Including the two things I mentioned here, risk and engage-ability, should easily fit into your definitions, though. And don’t be afraid to give them more flaws or take more risks than necessary. Most of the fun in tabletop RPGs comes from success against all odds or when everything hilariously blows up in your character’s face.