This is an interesting question. Usually, when we are talking about creating realism, or more accurately verisimilitude, we focus on the game master or the game material. However, the GM isn’t the only guy or gal at the table. So how do players aid in creating a realistic game world experience?

Top of the list, I’d say is Buy In. The players have to be interested in the game universe, and want to immerse themselves in it. That doesn’t mean going the full Jared Leto, but they have to want to believe in the rules, the physics, the history, the flavor of that world. In the immoral words of Ron Swanson, “Never half ass two things, whole ass one thing.” Whole ass that world.

That came out creepier than I though it would.

To that end, the players should take an interest in their role and what their characters might. For instance, if you are playing a 1930s globe-trotting adventuress with a love of aviation, maybe study up a bit on planes of the interwar period. What catches your eye? Are you a seaplane person? ’cause if you were, the flying boat is the only plane! Do you like functionality over beauty? You might be a Boeing 247 or Beechcraft Staggerwing person, and not so much the Lockheed Electra. Are you a hard-boiled detective? Research the basic laws of the setting (if possible) and structure of your police department. Are you a mercenary or a big game hunter? maybe know something about guns and/or game. Are you a wizard?

Players should have their characters interact with the other characters. The worst is when you get the min/maxed character that spends their time in their room “inventing” or whatever, and only shows up to chew bubblegum and kick ass. Are they friends? Are they frenemies? Lovers? We had two players’ characters hook up and get married. (And the players aren’t, to my knowledge, interested in each other. Which is kinda rare when you see this sort of thing in games, in my experience.)

Make suggestions to the game master. What about this kind of adventure? Can we do X? Is there a person who can get us Y? Help flesh out the world. Fortunately, this is a trend we’re seeing in some of the newer games, where your Session 0 is often putting these relationships together, or even helping to build the city or world together. All which creates buy in.