Science Fiction and Historical Fiction are generally perceived to be polar opposites, but they actually follow very similar rules. Remember that Science Fiction and Historical Fiction are merely settings that allow your plot to take place as you want it to. That means that you need to come up with your own conflict, you own characters, and everything else just the same as any other novel. The only difference difference is how you apply it to being in the past or the future versus the present.
Because of this, I only have a few main tips for Science Fiction, just like the last chapter. I hope you find them helpful!
1. What If
In futuristic novels, you must always think to yourself "what if". What if the sun exploded? What if man-kind developed a technology to bring people back from the dead? What would happen if there was World War 3?
This is where the plot will come from when writing in this genre. You have to explore what could be and all the different ways that society could go wrong if they continue along a path or if they decide to venture a new one. The most interesting futuristic plots are the ones that could potentially happen.
2. Present-Day Issues
Most futuristic novels use present-day issues and disguise them in an extreme, unfamiliar landscape. This has to do with the theme of your novel. Try and make a point about society. Take global warming, for instance. That is a present-day issue. Say humans don't do anything about it. How will our planet look in one thousand years, two thousand years, five million?
Aside from theme, the main character should face challenges that could potentially happen to someone in our day and age. The circumstances will change in your novel, but the emotions will stay the same. Think about that. If you present issues of the present in your futuristic novels, it will also seem more realistic to the reader.
3. Dystopia, not Utopia
You probably noticed a trend in YA fiction lately. All futuristic novels have some sort of dystopia.
By definition, dystopia is an "imagined place or state in which everything is unpleasant or bad". A utopia is the opposite.
However, authors have managed to blur the lines between the two by giving dystopian societies admirable motives but less than admirable ways of achieving their goals or by disguising dystopia's as utopia's. There is a reason they are almost never written as just a utopia and that reason is that it never works. Utopian societies are boring.
If you are writing a futuristic book, please make the society dystopian unless you have a really good reason not to. Nobody likes perfect; that may well be the greatest misconception out there. People like to read about people who rebel against corrupt societies, that make a change for the greater good -- no matter the costs. We enjoy seeing someone come to the gradual conclusion that something is wrong in their world and, even better, deciding they need to do something about it.
4. New Culture
The culture of your world will be probably the most obvious quality your futuristic novel. That means that names should be different, but please don't make them absolutely ridiculous or hard to pronounce. Remember everything I said in the last chapter: consider the economic and political state of the society, the state of the Earth, social classes/roles, and common beliefs or expectations. Another fun part is making up common sayings of the future.
There may be new technologies or, in some cases where the world has been ravaged, your characters might be starting from stage one again. Consider religion. Are people religious anymore? Is there a new religion? What is it? How does the government work? What are the new rules of society?
Remember that I only say these things assuming that there will be a society. If there isn't, such as in the case of an apocalypse, none of these things matter. In that case the issue might be that there is no order or that a plague is killing millions.
5. Underlying Secrets
Usually in a dystopian novel, the society is hiding a deep, dark secret of sorts. Make sure that your futuristic novel is more complex than meets the eye. Sometimes the secret is that the society's economy is failing or that there is an exterior threat that they can't defend themselves against. The secret should be revealed at some point. How your character reacts and what they do about it makes the story.
Example #1: In Divergent, Tris discovers that not everyone fits into a category; some people are Divergent. In learning this, she finds out the more cruel aspects of the Erudite and what exactly they plan to do to those they can't control.
Example #2: In "Matched" Cassia finds out that the society isn't perfect and their system is actually flawed, unlike what she had been taught to believe. She discovers what it is like to have a choice in her lifestyle and how far she would go to take control of her life.
6. Planning and Researching
Science Fiction is a huge genre for research! Although you don't have to be a technology whiz, if your story has it you should have a basic understanding for how it works. You should also be knowledgeable on the politics in your story and how everything works. Make sure you plan out everything, even if you won't use half of it in your actual story. I have a chapter on both planning and researching. It goes into depth for both.
Sometimes dystopian authors think that since it's the future and it hasn't happened, they can do anything they want. That isn't true; you still have to follow the law of physics and realize when something isn't possible. Humans can't mate with animals to create a new species; it just won't work. Although I can't imagine why anyone would want to write that; it sounds rather disturbing. Anyway, the point is that you should save the impossible for your fantasy novels. There's a time and place for everything.
That's all! I highly suggest you read Science Fiction novels so you get a better feel for the genre. If you have any questions, please ask. Thanks for reading!