Yes, everyone knows, Star Trek isn't real. But the universe in which we SIM has it's own "rules" that we have to abide by. These rules include things like we have in real life: gravity, death, etc. It also has rules that we don't have, like what the top speed of a Galaxy class ship is, or just how much damage a photon torpedo can do. If when you're writing a SIM, you're putting in something that doesn't exactly fit into what you would see in Voyager, Deep Space 9, or The Next Generation, then you probably shouldn't be putting it in.
So, for example, if we were in a battle plot, you should only be putting things in that would happen in a battle. This isn't the time to be trying anything experimental, like start you character on a workout regiment on the holodeck. Doing such a thing is out of the scope of realism, for a few reasons: A) Your character, no doubt, would have more pressing issues on his/her mind during a battle, like how to keep the ship working. B) Power on the ship would be diverted away from holodecks and other recreational areas, during a battle.
Realism & the Plot
For some reason, many SIMmers seem to forget that they are taking part in a collective writing experience. SIMming is like writing a collective novel. Everyone controls their characters, and takes part in driving forward the plot. But plot is a tricky vehicle to drive, and it takes a lot of practice to be able to steer it with pazazz.
If there is one thing that everyone SIMmer should understand is that without a conflict, there is no plot. Story-writers through the ages have defined a number of "stock conflicts", that just about every story you read or watch follows. The generally accepted conflict arcs are as follows:
Why is all this important to SIMming? Because as you can see above, all good plot arcs involve a conflict. The most important thing to remember is that conflict is what makes all of this fun. The purpose of studying conflict is to know why we have to ensure that conflict is cultivated, fed, and resolved in an interesting and meaningful way.
Some SIMmers seem to have difficulty in understanding why conflict is important, and sometimes resolve the conflict too quickly, and/or too easily. When this happens, it destroys the flow of SIMming, and much repair has to be done to the SIM. SIMming in a way that resolves conflict too easily is often called "Super Gaming". Let's say for example that our typical heroic crew was in a battle with two Romulan Warbirds. A typical Super Gamer would fire a full spread of torpedos and destroy one, or both of the Warbirds within the first five minutes of the battle. Now where's your conflict? Somehow (against the rules of Star Trek, which is that all the Warbirds we've seen have been at least as powerful, if not much more powerful than any StarFleet ship), the crew has managed to destroy these ships, thus effectively ending the plotline there. Now what? See the problem?
Generally a good rule of thumb is to consider: Would this happen on "Star Trek: The Next Generation"? Would the Enterprise have defeated a ship in just one or two phaser blasts, or torpedo shots? Was Geordi able to stop the warp core from breaching within 30 seconds of hearing the alarm, every time? Was Picard able to persuade every alien race to do it his way? If you keep this in mind, it will be much easier to SIM a realistic plotline.