One of the hardest things to do in some games is to get everyone involved. By that I don't mean playing the game - just by showing up they will end up playing - but rather to get their characters hooked and involved in a plot that engages the player.
Some PCs make it easy, jumping in to anything and everything that is happening with joyful aplomb. Others make it harder. They stay quiet and near the fringes, their characters only really showing up for combat and mechanics but otherwise keeping to themselves.
Today I want to talk about how we fix that issue, and get the person involved.
It Takes A Conversation...
You've identified a player in your game that you want to get more involved with things, but aren't fully sure how to bring it about. Well, lucky for you it is easy. You just need to talk to the player. Do it in private if you can. Ask them about the game, ask them if they're having fun, and ask them what they are hoping to get out of the game or their character.
They may not know at first. That's cool, sometimes we don't know what we want, but talk to them about it. Offer suggestions or directions they could go, tell them what interests you about the character, and find out what they like most about their character themselves. Once you've talked about it, move the conversation onto the next step.
And Three Items To Focus On
Once you've had some brainstorming time you want to focus on the conversation on these three things:
What does the person want out of the character?
This is the whole point, but try to have them come up with an answer. Even if it is just to be the best doctor they can be, or to gather all the XP they can get. Find out what kind of stories they want to be involved in and see happen. Find out where they see their character ending up in 5-10 years. Ask how they could see their character dying. Talk to them about it all.
What do they need from you, the GM, to make that happen?
This is the part of the conversation that some GMs have problems with, but it is important. Figure out, together, what you can do as the GM to help bring about the things the player wants. They want to be the #1 duelist in the Empire? You as the GM need to provide them opportunities to duel and people to duel against. They want to be a mad scientist that collects doomsday devices? They need to have a chance to develop or steal those types of devices. These are things you can do as the GM and basically from this part of the conversation you are getting ideas for themes and premises for plots this character's player wants to be involved in.
What do you, the GM, need from them - the Player - to make this happen?
I've seen this part take players by surprise, but it is every bit as important as the point above. What does the player need to do to help make these things happen? That person wanting to be a great duelist needs to answer challenges for duels, train in dueling, and likely stop fleeing from every combat that tries to form near them. That mad scientist can't go around destroying all research notes and documents around them, and needs to spend time developing and testing there advancements towards the doomsday devices.
The crux of all this is that once you and the player discuss what you want to happen, you both need to be willing to work to it. The GM needs to provide the opportunity and lay the bait. The player needs to be looking for chances and take the hooks where they can. Only together can it work.
Good luck, and have fun!