Some actions cannot be performed for reasons of safety or reality but must be considered as taking some time to complete. Such actions will have a specific count, usually three, and a definite phrase to indicate what is happening.
For example, to simulate an Undead rising from a grave, the Cast playing the Undead might say “I rise from the ground one, I rise from the ground two, I rise from the ground three.”
During the time in which the player is saying this, they are completely vulnerable to attack and cannot use any game Skills other than defenses. Using a defense from a Skill or Monster Ability will cause the counted action to be interrupted - the Skill or ability is used up, and the count is terminated and must be started again. Dumb defenses such as Spell Shield or Weapon Shield do not interrupt a counted action in this way.
This type of counted action is used primarily when the Cast are within visual or aural range of the players who can then try to affect the monsters. It should only be used when it must be made clear that the Cast is taking some sort of action that the player would not be able to observe or understand otherwise.
Cast who have already come IG away from the PCs do not need to announce their presence with a counted action like this. If you are far enough away that it will take at least three seconds to reach the player, you should not announce your presence. In most cases, Cast should come into game far enough from the PCs that they emerge naturally onto the scene.
Players do not need to use “counted actions” for every action they wish to perform. They are needed only when a Skill or ability specifies such.
Counting actions is OOG and discouraged unless (a) you are performing an ability that has to be counted; or (b) you are IG performing an action that you are not really performing OOG and you are aware that you may be attacked while performing this action.
To better explain (b), imagine that you want to climb down into a cave. If you are in a location where it is safe to climb down into a cave, there is no need to count the action as you will be physically climbing into the cave. If instead a Marshal says that IG, you see a cave entrance, and entering it will require moving OOG to another location, then you should use a counted action to represent the activity of climbing into the cave entrance.