%USERPROFILE%\Documents\Paradox Interactive\Crusader Kings II\A Game of Thrones\
Press ~ (or the equivalent key above Tab ↹ on your keyboard) or Alt+Numpad 2+Numpad 1 in-game to enter console commands.
Alt+Numpad 2+Numpad 1
If your activation code is too short for the code input box upon installation, fill the additional spaces with the character 'X', e.g. for a code formatted as AAAAA-BBBBB-CCCC you would input it as AAAA-ABBB-BBCC-CCXX-XXXX-XXXX.
Your game version is given by "CK2 v<version> (<checksum>)" (for example, "CK2 v1.06 (YYEV)"). After enter a singleplayer or multiplayer game, it's possible for the checksum to change in some PCs (for example, to "CK2 v1.06 (ZYEV)"), while the others keep the same checksum. This won't allow you to play in multiplayer due to incompatible versions.
Restarting the game fixes this problem.
Most mods also change the checksum, so you may not be able to join the host if you do not have exactly the same mods (including same version) as the host.
Since the introduction of the new launcher, alt-tabbing out of the game and back into it changes the system resolution and consequently makes the game unplayable. This can be prevented by bypassing the launcher via a terminal command. The command, in its simplest form, is:
Additional arguments are:
A third-party free software launcher is available that does these things for you.