Let me start by saying that I’m not advocating that you run an actual background check on your players (although if you met someone in your group online or through a bulletin board at your local game store or something maybe that wouldn’t be a terrible idea).
I’m talking about doing pre-session “roleplaying warm-ups,” which I’ve written about before. The basic idea is that before each session, you ask each player to describe something about their character or an experience they have had in the past, or something about their goals, or even how recent campaign events have impacted them. The idea is to get them thinking about their character, in character, in a way they may not have thought about or have thought about but they haven’t had a chance to share that information with the group. It should be something fun and quick, that helps the player flesh out his character a little more while getting into a roleplaying frame of mind.
Backgrounds in Dungeons and Dragons 5e are perfect for incorporating this exercise into your game session, and are an especially good area to pull ideas from for early on in the campaign, even the first session. Have the player’s come up with some small tidbit about their character’s background. Is the character an artisan? Have them describe who their mentor was or who they apprenticed with. Do you still have a relationship with that person? Did they impart any life skills or moral leanings on the character? Was the character an acolyte? Did they make this decision themselves or were they perhaps the youngest child in a large family, with acceptance by the church being a way for the family to reduce its financial burden. Does the player have the urchin background? Have the player tell you about a time when they were hungry. What did they do? Steal? Muck stables?
These are just the ideas that came right off the top of my head for a few arbitrary backgrounds, but hopefully you get the idea. Try and come up with something that not only makes the player think about their character in a way they may not have, but also adds something to the character by defining some aspect of their personality or moral code. Once the player starts talking, ask some probing questions to keep them thinking, but keep things relatively short and simple. There are no right or wrong answers and the player shouldn’t feel pressured to come up with rich details at this point. Maybe they will add some details later though, after they have had some more time to incorporate what they came up with into their idea of the character, and that’s great!
This is also an excellent time for you as the Dungeon Master to share little bits of information about the campaign world with your players. At the beginning of each session, after your question and answer with the players about their characters, you should share some interesting bit of information about the campaign world that would be common knowledge to the players. Disseminating background information in small chunks like this should help your players retain the information more than they would if you read them pages and pages of background information about your world all at once. Each week, pick an interesting thing about a noble family or a kingdom or a city or a religion and share it with your players. Keep it short, simple and relevant to current campaign events if possible.
I’ve fallen out of the habit of doing this in my recent games and there is no excuse for it. That’s a shame, because whenever I’ve done this, my players have really liked it. So next session we’re discussing backgrounds before we play.