To roleplay a character with any degree of accuracy, it is necessary to distinguish between what information the character knows, and what information the player knows. In this case, such is similar to an actor in a play or movie-the actor does not cease to play his or her role, even if a gruesome fate awaits the character, and, even knowing this, still acts out surprise (if appropriate) when such a fate comes to pass.
In roleplaying, the same type of separation is necessary. To some extent, you may "know the script", or at least have some guesses as to how it will play out. However, this does not mean that your character is aware of this information. Therefore, the first thing covered will be how to separate OOC from IC information. (Some players may be more familiar with the terms "player knowledge" and "character knowledge". For those familiar with these terms, IC means character knowledge, and OOC indicates player knowledge.)
The terms "player" and "character" knowledge do describe an accurate manner in which to separate OOC from IC knowledge. If you, the player, know something (perhaps from hearing it said on an ooc channel, or hearing it over an instant messenger service from a friend), that is OOC or player knowledge. Your character has not heard of this information "in character", and so should take no action on it.
For example: Your character, Kielen, is acting as a spy for the New Republic, while maintaining membership in the Empire. A friend of yours (who is not IC'ly involved in the roleplay at all) sends you this message via an ooc channel or instant messenger: "Dude, you're dead, the Emperor figured out what you're up to." This is rather disconcerting, as you are due for a strategy meeting with the Emperor today, this is how you've been doing your spying.
What is the correct way to roleplay this? Unless your character has some in character way to know this, the correct way to roleplay this situation is to attend the Emperor's meeting as normal.
No doubt about it, the death of a character you've grown attached to, built up, and played for weeks, months, and even years is hard. This is something I know well, from the pencil-and-paper games that I play. Cloning certainly can ease the sting (when a character dies in a pencil/paper game, it's gone, write up a new one, have a nice day), but it is still difficult.
However, to extend our previous example, consider the following resolutions to the message sent to Kielen's player.
The cast of characters:
Kielen, the New Republic spy.
Jamison, a New Republic lieutenant.
Marken, the Emperor.
(Kielen): You tell Jamison: ooc dude open the MC90 for me, I'm busted.
(Jamison): You tell Kielen: ooc what's up?
(Kielen): You tell Jamison: ooc the emperor knows I'm spying I'm going to get killed.
(The Empire)Marken: Kielen, do you expect to be here shortly?
(The Empire)Kielen: Yes sir I'm on my way.
(Kielen) You tell Jamison: ooc thanks I'm landing now.
Kielen has resigned from The Empire!
(OOC)Marken: ????
(OOC)Kielen: you know you were going to kill me.
(Flame)Marken: that is such bullshit you didn't know that IC.
(Proceed here to a large and ugly ooc fight that results in someone getting helled for a while.)
(The Empire)Marken: Kielen, do you expect to be here shortly?
(The Empire)Kielen: Yes sir, I'm on my way.
(Kielen enters the strategy meeting)
Kielen bows before Emperor Marken.
Emperor Marken nods toward Kielen.
Emperor Marken grins evilly.
Emperor Marken nods slightly "Good evening, Kielen. I've brought you here to discuss a grave situation."
Kielen asks "Yes, sir?"