Choice. Part 1?

Choice is the driving mechanic of ATOMIC.

A choice, by nature, revolves around conflict, internal or external. Choice is evident when there is uncertainty in a situation. Do I drink my water now, or ration it? What perk should I pick up? Do I wait to see what this guy has to say, do I shoot him in the face, or do I hide until he goes away? There is uncertainty in any of these questions, concerning short-term vs. long-term benefit, motivations, potential, choices between things with very few common factors, even the future. Making a choice is different from solving a problem, which is about calculating the most beneficial course of action, about answering the question "correctly." All other factors being equal, do I take the gun that does 3 damage, or the gun that does 5? is a problem to solve, not a choice.

Choice is impossible without a clear idea what is going on in the world around you, but, like life, you generally don't have all the information. If you have all the variables clearly laid out, you are making a decision, and that isn't what we are aiming for here. To this end, here are a few things that should be common to most games of ATOMIC, and ideally, most RPGs in general.

• The GM will give you whatever information is necessary for you to make meaningful choices. This does not mean the GM will detail things to an excruciating degree, only to the extent that you can make informed choices. This can be a balancing act, and the GM is sure to louse it up occasionally, but generally speaking, you won’t be bombarded by walls of exposition, but you also won't have to imagine you are in an endless white room, either.
• The GM will not just hand out information that is not critical to a basic understanding of the situation. If you are hunting for clues, for instance, the GM will have provided a description of the area (or person), and it your job to investigate more closely. Ask questions, experiment, use your skills, it's up to you.
• The GM will not tell you information you would not be privy to in your character's position. You won't be able to tell what someone is thinking or what their motivations are and you won't be able to predict the future. The GM won't tell you what lies behind the locked door unless your character has a reason to know such a thing.
• The GM will use your character's knowledge (measured by skills and general IQ) as a guideline for helping you assess probable outcomes of your actions if you ask. If you contemplate making a 30-foot leap between skyscrapers and you ask the GM how it could go, s/he will probably tell you that you will get a very brief, instructive lesson in human aerodynamics and become a permanent part of the landscape below. The GM will not simply volunteer this information. You need to ask, otherwise it is assumed you are thinking through the process on your own.
• There will be a good bit of discussion at the table. Not only is this the normal activity of a role-playing game, in ATOMIC it is also a way to engage everyone at once. This is not an invitation to argument, nor to senseless debate about minutiae. This is about collaborating in the construction of a cool story, and it is in everyone's best interest not to be selfish or steal the spotlight or argue about "what the rules say." Saying it right here: If a rule gets in the way of everyone having a good time, ignore the rule. This is a game, and we are here to have a great time, and while some people really enjoy debate or even argument, most people would prefer to do something else.
• The choices you make matter. The wasteland has a long memory, and a million stories to be told or discovered. No adventure in ATOMIC is so sacred as to force you along a particular path to resolution, or even to pay it any heed at all. No location or person is so important that you can't blow them to kingdom come. You choose who and what is interesting to you, and see what comes of it.  GMs: This is not a sideways method of encouraging you to punish players who kill off your pet NPCs (and why do you have those anyway?!) or just won't bite on your quest hooks. DON'T DO THAT. You shouldn’t be selfish or steal the spotlight, either.

 
Daniel Floyd and James Portnow have been a huge influence in the design process for ATOMIC. Here, they discuss choice, its nature, and its place in games. Here is a newer treatment of it on Penny Arcade. The context is video games, but the concepts carry over into RPGs, and particularly (like I just noted) into ATOMIC.