You can try to do anything to someone, but they control what actually happens to themselves. Never deny someone a chance to react, no matter what you do. Before you post your action, consider what you have written. Do you directly affect someone with it, adversely or positively? Do you block them off from some options that someone would normally have in their situation? If the answer to either question is yes, you probably need to revise your action.
However, just as bad as taking control of someone else's character is making your own never get affected by them. Therefore, you should let people at least achieve SOMETHING when they attempt to affect you. You don't have to all the time, but if your character is continually "immovable" you will be godmodding, and people will be extremely likely to ignore you. So don't just "I dodge" everything, okay? Let people do something to you if they try.
Each character has one skill, one thing, that they can do perfectly. When making a character, you select their Perfect Skill. There are no rules about what is or isn't a valid Perfect Skill, but don't be a jerk about it.
Unlike normal actions, using Perfect Skills let you directly effect someone without their permission. However, beware. They might override you by spending Fate (see Fate). Killing another character with a Perfect Skill is not allowed, so don't try it.
In this game, defence takes the lead. When an unstoppable force meets an immovable object, the object stays still. The perfect hunter doesn't find that which is perfectly hidden. The perfect defense will stop even the perfect attack. I think you get the idea.
When one character says they are trying to do something and another character wants to stop them, they can initiate a conflict. The player who was attempting an action is called the Actor or Active Player. The player who objected to the action is called the Objector or Objecting Player.
The Objector declares a set of two possible outcomes, [emphasis]without stating who gets which outcome.[end emphasis] At least one of the proposed outcomes should achieve the action or some piece of the action the Active Player was trying to perform when the conflict was called. When declaring the possible outcomes, the Objector must make both sets of outcome possible to apply to either character involved (e.g., you cannot set the stake of "one PC becomes pregnant" if male characters are involved, unless magic is involved in the bizarre male pregnancy.)
The Active Player in the conflict decides who gets which outcome. The Active Player’s character suffers one of the outcomes, and the Objector’s character suffers the other outcome. These rules should encourage the framer of stakes to set stakes that are each a mixed bag, or that tempt their opponent into abandoning their current goal for the other option in the conflict. The rules should work like trying to get greedy children to cut a pie: one cuts (i.e., sets the stakes), and the other chooses.
Character V World:
Characters automatically succeed at tasks unless another character is trying to stop them in some fashion.
A player can have up to 3 Fate at any time. (Side note: Each player has only one Fate total, no matter how many characters they may have.) If you think given action is awesome enough, you can call to give them Fate. If someone other than you or the person you are calling at seconds this call, the person you are calling at gains 1 Fate.
By spending 1 Fate, a player can allow a character to (it doesn't have to be their character):
-Act perfectly outside their Skill for 1 action (as if they had it as a Perfect Skill)
-Perfectly stop another players action against them (as if they had the right Perfect Skill to stop it)
-Reject the stakes in a conflict, setting your own instead.
The Weaver is a special player, tasked to keep order, and stop people from ruining the game. They have several special abilites to help them do this. (NOTE: the Weaver is still a player, and can still have characters, and their own fate pool.)
-Weave: The Weaver has access to a second pool of Fate. This pool is infinite in size, but they cannot use it for their own characters.
-Veto: The Weaver can declare a given Perfect Skill forbidden. Any characters with it must pick a new one. No future characters can have it. Any number of skills can be forbidden. (The Weaver can also reverse this choice, allowing a previously forbidden skill to be chosen again.)
-Elevate: The Weaver can declare a given player to be his Proxy. Proxies have access to, and can use, the Weave ability. The Weaver can have any number of Proxies. (The Weaver can also reverse this choice, stripping a player of Proxy status.)
Most of the text about standard actions is from: http://ow.ly/eSyQv
The idea of Perfect Skills along with the idea of defences taking the lead comes from Perfect Defences in Exalted.
The conflict system is stolen wholesale from House of Masks, a really fun game you should try, by Nick Wedig: http://ow.ly/eSukY