One thing it is too easy to do is to polarize people as dove’s or hawk’s. As people who want war or peace.
Few men are really going to be always for one or the other. The most ardent hawk will not want a war that he can’t win, and few doves will want peace if it would cost them the lives of everyone they know and love.
One exercise is to ask yourself what would cause your character to cross that line? What would cause your man of peace to go to war, or what would cause your man of war to sue for peace?
One thing I think Star Trek did well is show men of peace who are willing to go to war. Spock hates war, and would do his best to council against it or stop it, but there would be times and places it would be the only option and he would lead the charge. For example when it becomes clear who the Romulans are, vulcan’s who never embraced logic and who left home long before, he says war is the only way.
Kirk is more warlike for sure, and walks to the line more often then spock does. But even so he never likes it, he sees force as a last resort, but nonetheless it IS a resort.
One of the first thing you are taught when learning programming or game design is that complexity is the enemy. Its the price you pay to add the stuff you need to your project. I have found this holds true for any large project, including novels.
Every character you add, every new technology, everything makes things more complex. This is not to say you should not add more characters or add more technology, it means you should do so only with good reason.
To be clear, “It makes the setting feel more real,” is a perfectly good reason to add something. But you need to have SOMETHING to tell you to put it in, everything you add could bring new problems.
Think about the best movie you have seen, were there any wasted scenes? In most really good movies most scenes do several things at once and everything they do is necessary.
If you have read much science fiction you at least know of John Carter and Barsoom (AKA Mars).
The stories are not really science fiction as we would think of it today, but sword and planet. I find them interesting partly because they show how far science fiction has come.
While the books do not have the deepest characters what they do have (particularly the first couple) is a level of world building I hope I will one day approach.
The stories have people that are often brutal, different in ways its hard to imagine but who you feel sorry for. They invoke a feeling of wonder, of meeting people you can admire, or hate but will never really understand.
Honestly its hard to quantify how Burroughs did it, but it works and it does so with seaming effortlessness.
The main character, John Carter, also does something I wish more characters did in fish out of water type situations, he accepts the people he finds as they are and acts according to their value system when he has to. If this means killing that is what it means
One question you should ask yourself as your planning any science fiction story is why is it science fiction? Why not set it in the here and now?
Making something science fiction adds word count, it adds complexity, it adds a lot of work. Could this story be told without the science fiction elements?
If the answer is yes, then don’t make it sci-fi, if no then your good to go.
Besides wasting words this can be a problem because when people read science fiction they want to read stories that can’t be told any other way. They want to read about problems and solutions that could not happen today, about ways of looking at things that never occurred to anyone in the hear and now. Your going to disappoint them if you write a modern story where the backdrop and only the backdrop is science fiction.