When can you tag an aspect?
Does it need to be your turn? Do you have to do it before or after an action?
You do tags (and invokes) as part of an action. There's no before or after; it's integral to and internal to. I suspect you're asking if you have to do it before you *roll*. I normally allow it both before and after the roll (and our rules may support that position, I forget).
It doesn't need to be on your turn, because defenses aren't, and you're allowed to use aspects when rolling to defend.
For example, you do a maneuver to put the "prone" aspect on an NPC. At his action he tries to run away, can you use your free tag to invoke an effect or consequence to prevent him from fleeing?
I'd allow that. Then again, as the GM, I wouldn't even allow him to try to run away; I'd have him spend his action on removing the aspect.
Another example, you put the "on fire" aspect in an area with some explosive material. Can you use your free tag (for effect) right after to declare that the "barrels of chemicals" explode? Essentially turning your maneuver into an attack?
I like this idea. Does your GM?
And as a game master, how do you play the aspect put on your npc? Do you give them Fate points everytime you act in a way consistent with the aspect...such as if it would have been compelled?
Might give 'em one, but I wouldn't do it every time. Payouts should occur only when the aspects have a significant impact on the character's actions.
