Before the first round of combat, the players declare their intent and decide the order in which they want to go. The GM privately decides what the combatants under his control will be doing and the order they want to do it in. This order may change throughout combat depending on what takes place. The GM, although he may be controlling some characters in the battle, must decide this logical order with fairness to both his team and the player-controlled team.
Characters who will be performing regular actions do so in the order decided for them. However, outside of this, many other actions may be taking place that could change the order of combat. A gunman, for example, who has a rate of fire of three may fire at the beginning of every third round. If more than one gunman can go, they go in the order of highest to lowest Reflexes scores. Once all gunmen have gone, the character whose turn it was may go.
Also, a character who has built up enough power to cast a spell or use some other similar power can go at the very beginning of the turn on which he builds up the amount of power needed, before the gunmen. If more than one magician's turn comes up in this way, the magician who started casting his spell first gets to finish casting it first.
After magicians and ranged combatants have gone, the character whose turn it is may make his action. He may move, act, attack, or do whatever action he cares to take on his turn.
Normally, the GM would ask what order the party wants to go in, and decides what order his group is going to go in. He would start with a character on the team that initiated combat, and then alternate back and forth. However, in the end, it is the GM’s decision as to the order in which combatants go, based on who he believes would logically act next. When he says it is your turn, GO!