This will be an abbreviated review of what represents my thought process when creating a world for a game-oriented script. I will run down the basics of the points that I hit when I write.
Every writer has a specific thought process before they sit down and map out what they want to do for a story. They know that whatever kind of script they write, they have to make sure that the story is fitting for that genre. As a writer, in my opinion only, I feel that one should have a basic plan of attack as to how to create the world of a fictional story. It won't be easy, but it's also not rocket science.
1) Characters - What do you want?
First off, we need to know what kind of story we want to make and what would be a better way to start off your story than to think of a character you can build your fictional world around. The main characters that you will have for your stories will depend on what kind of worlds those characters will be in. For example, if you are aiming to have a character in a realistic and serious tone, then you would most likely make up a character that relates to heroes from the movies; John McClane, Riggs and Murtaugh, John Quincy Archibald, Roy Hobbs, etc. If you are aiming for the cartoon feel, such as the laid back, colorful and free roaming environments, then you would most likely be focusing on characters in the Video Game Industry like Mario, Sonic, Crash Bandicoot, Sly Cooper, Rayman, Kirby, etc.
2) What is the world of your story?
This can be interchangeable with #1, but really both are equally important. Some stories involve the world revolving around a character, but other stories involve characters that revolve around a defined world. In some fictional worlds there are specific rules to live by as far as gameplay goes, and the personalities of the characters sometimes take after the situations that they are put in. The worlds your characters inhabit affect them in some way. Remember that. It's wise not to disregard the world your character lives in or else some problems may arise. Is this a realistic world you can see people on Earth living in? Is this a cartoony world you can see mascot-like characters living in?
3) What is at stake?
There is always a carrot to dangle in a world and in front of the characters. As a writer, you need to define what that carrot is exactly. What is the main thing that the characters just can't go without? What do they stand to lose if they don't have this main thing? How important is this main thing? What exactly is the situation? Who are the major players in this game that are causing this main thing to be at stake? How should the player who controls the main characters care about what's at stake?
4) How will you bridge the gaps in storytelling?
When you get somewhat deep into storytelling, what will be the thing to keep the players emotionally invested in your story once you have grabbed their attention? What can you do with your storytelling that will make players go "Hmph! That was interesting! That sounded like a curveball! What did "So and So Character" mean by saying that?" Knowing how to bridge the gaps from one scene in the game to the next is critical. You don't want to rush and slap every interesting nook and cranny into just a few scenes, but you also don't want to drag the player through an imaginary creative desert neither. You have to find some sort of balance. You have to pace your style of writing.
5) What will the player identify with? (Symbolism)
This is my personal favorite weapon of choice in my writing. Symbolism. There are various uses of symbolism in writing stories. An object, a place, a person or an event can all be used as symbols for the story you are telling to the player and the beauty of symbolism is that you can use symbols to change in their meanings. Throughout the progression of a game's story, that one iconic thing that represents the symbol can change ever so often. It can mean one thing between a boyfriend and girlfriend scenario, but then change into a symbol of teamwork between members of a gang, and then change into a symbol of reassurance to a struggling community of people. The more flexible a symbol is in a game, the better chance there will be of a player recognizing it and remembering it for future reference, and perhaps for a possible sequel of that game.
These are just the basics, in my opinion, of what a writer should know when he or she digs into storytelling for a game script. You have to relate to the gameplay mechanics when you write, but you also have to be mindful of the fundamentals as well. Make sure that your story connects, relates and executes and you should move forward with your projects well.