When the dragon stirs or the guards raise the alarm, it really matters when you can do what. Action scenes are exactly what they sound like -- fast paced moments that you might see in an action movie or video game. While in movies or video games, action scenes are often fast paced and happen in real time, Action scenes are turn based to allow players their space to contribute to the narrative. There are some things that are broadly applicable to all kinds of action scenes, but sometimes you may want to slightly tweak those rules to better convey the feeling of different types of scenes -- a battle will feel differently from a chase, for instance.
Who goes when
Since they're usually taking place in a short duration of time, everyone and everything that impacts the action takes their time in the spotlight by taking turns over the course of one 10 second round. Of course, it's possible that the length of a round may vary depending on what kind of action scene you're in -- a race around the world, for instance, might instead have rounds that take place over days or even weeks.
The following is adapted from the ruleset designed by Fred Hicks on his blog post Accidentally Designing Marvel’s Action Order System which has since been removed -- linked is a reprint of the post in the FATE SRD.
The first round of the action scene, figure out who made the first move. Almost every chase starts with someone bolting and almost every battle starts with someone firing the first shot. Whatever that action was, play it out and let them take the rest of their turn if they still have more to do.
Then, after the first person to go has finished their turn, they must choose another character or obstacle in the scene who has not taken a turn yet this round to take the next turn. This includes characters who so far haven't contributed to the action scene, introducing them to the fray. If there's nobody left who hasn't taken a turn yet this round, congratulations! You're the last person in the round and you get the strategic advantage of being able to pick anybody in the scene to start the next one.
If you have a special ability that lets you do it you can interrupt the turn order, taking your turn in place of whomever was originally being passed to. If you do, at the end of your turn you may choose whomever you want to take their turn next -- you don't have to pass the turn order on to the person who was originally going to take their turn.
Who do I pass to?
At the end of your turn, you're going to be faced with a choice -- who do you want to pass to? Sometimes the answer to this is just "who does it make sense to pass to"? If you're having a tense 1-on-1 duel with an enemy, you might want to make your move and then pass to them to keep the back-and-forth going. Sometimes the answer is teamwork! Maybe you set up a teammate for success by creating stacks for them, or they let you know they have a great follow up for whatever you're doing.
Passing to an enemy seems bad on its face, but actually has some strong tactical value. By passing to an enemy, you get to see what they'll do during the round and be more able to react to it. In addition, sometimes passing to an enemy can secure your team ending the round. Used cleverly, this can allow some key characters the opportunity to take two turns in a row-- one at the end of the round, and one at the start of the next round.
Whenever you do something with a goal in mind, you accomplish it with one or more actions. If there's drama involved (and there often is), the actions will probably also include a test and you'll roll dice to see how the action resolves. Most of the time, your actions will be using basic or special abilities
When it's your turn, you can take up to 3 actions. If you want to do something but you don't have enough actions left on your turn, you can start it on this turn and finish it once all of the actions required to complete the goal have been spent, even if you have to split it up across turns.
One action on its own measures accomplishing a quick goal like throwing a punch, moving behind a pillar, or triggering a mechanism. Multiple actions in a row are how you do time consuming or difficult things like pushing over a statue, disarming the security measures on a door, or reloading a siege weapon.
If a task requires multiple actions and it makes sense that many people can be working on it, each person involved can contribute actions to its success, but if you stop in the middle and nobody spends at least an action on that goal in a round, your GM may say that your progress is lost and those actions were wasted.
Defining scene-specific actions: chases
Sometimes it can be helpful to define specific actions that can be taken in an action scene. Chases, for instance, are a special kind of action scene that capture the fast back-and-forth between participants as they race towards the goal. Because distance towards the goal is the primary focus, there are several special actions that deal primarily with that detailed here.
Freeform action scene
The tide of lava rises, the rope bridges' tenuous connections begin to sever, the toxic gas flows under the door and across the room-- there are many times when observing strict rules for an action scene would get in the way of the drama of the scene. A freeform action scene is any action scene that uses some, but not all, rules that are normally a part of an action scene. There may or may not be any defined actions or even an established turn order. This allows each character the freedom to act as would make sense to the scene.