Cpt Author : The USS Narrative is approaching the planet Vulcan to pick up diplomatic representatives for a major conference. Begin Sim
Cpt Author : ACTION : A Romulan deloaks off the port bow!
Cdt Data : Romulan decloaking off the port bow!
Cpt Author : Red Alert! Worf, target the Romulan!
Cpt Author : ACTION : Sensors detect intruders in the engineering hull!
Cdt Worf : Intruders in the engineering hull!
Cpt Author : Modulate shields! Intruder alert! That Rom has likely beamed a team aboard!
Cpt Author : ACTION : The warp core is going unstable. The engineers don't think they can hold it any longer...
Yes, the above is an exaggeration, a parody. Among other things, the captain is typing twice as many lines as the rest of the ship combined. Unless the captain has the typing speed of The Flash, the cues given the players to establish the story line will be much fewer and broader than shown above.
While Paramount's professional Star Trek movies and shows have true fixed scripts - with every word uttered by the actors written in advance, and a director to specify how the lines should be spoken - simming is a form of improvisation. Even in the stricter style which I'll call fixed script story telling, the captain can only set a broad pattern with action statements and orders. It is up to the rest of the crew to follow that pattern while providing details, dialogue, and emotion.
Jazz music is another improvisation style. Yes, you have far more freedom in jazz than in classical music. However, you still have to listen to the rest of the band. You have to know who is keeping the beat, and stay with him. You have to know the chord progression, and keep your improvised melody complementing the chords. You have to know when it's your turn to cut loose, when you should be quietly maintaining the chord progression, and when you should fall silent to give others the foreground. If the final chorus of a jazz piece has everyone wailing their solo, this is music, not noise, only because each solo dances around the same rhythm and chord structure, and because the audience has heard each part featured during previous repetitions.
There are rules to improvisation while you are a part of a team. Different sim groups use different rules. Some of the common rules that might apply to many of the more structured ships follow.
"Push the Captain's plot line. Avoid going off on your own." A good captain should try to get as many departments involved in the main plot line as he can. He can't always involve everyone. Sometimes a department will be left idle for a time, and will have to create it's own subplot. This subplot should not interfere with the main plot, should not distract too much attention from the main plot, and should be quickly resolvable should the department suddenly be needed to advance the main plot.
"No ships decloaking, hull breeches, warp core ejections without permission of the captain." If the captain is planning a high speed chase at the climax of the adventure, the engineers must not eject the warp core early. Again, private subplots or department subplots may not interfere with the main thread.
"Report through you chain of command, not direct to the captain." The captain can't listen and respond to twenty people at once. He can, sometimes, sort of, with the XO's help, manage the bridge crew and department heads.
"A department head's job is to delegate." The department head is usually the only member of the department communicating with the command staff, and the only one giving orders. He should not also be taking the most interesting jobs. He should be keeping the assistants busy and coordinated, which is often a full time task. Only when all his assistants are occupied should a chief end up getting his hands dirty. A chief should also keep his people focused on the main plot if possible, and generate a harmless sub-plot if there is no immediate way the department can contribute to the main line. Also, given that the assistants are not supposed to be communicating with the captain, the chief should be listening to his assistants, implementing their ideas, and passing them up to the captain when appropriate.
The above suggestions are most appropriate for large ships where the captain is keeping firm control of the plot. To some degree, they are useful in other styles of ship as well. However, the first problem is figuring out what style of ship you are on. Does everyone have action authority, or just the captain? Is the plot fixed and controlled by the captain, or is he presenting the players with a problem?