How to Write Science Fiction?

Steps

1. Find a general topic; this applies to any book. To write science fiction, you need to know a little about science fact, so search for your topic in modern science books, articles and magazines, or talk to a scientifically-inclined person.
2. Ask yourself "What if?" Remember, this is fiction. Play off your main scientific topic, but you can get a little crazy with it. For example, science can't really successfully clone humans yet, but what if it could?
3. Decide what your main conflict will be: Man vs. Technology, Man vs. Man, etc. Technology is a common enemy for science fiction books (as well as aliens), but don't be afraid to step out of the box.
4. Decide your setting and time period. Most science fiction happens in the near future and involves more than just planet earth, but there are lots of different types of science so don't feel bound to this scenario. Remember to stay within the limits of the time period you choose--if you choose only five years into the future, for example, we probably haven't developed flying cars yet.
5. Choose your characters, then write your basic outline. If you're not an outline person, then go ahead and dive into the first chapter or prologue. Good luck!

Tips

• You can combine several different ideas to base your book around; you don't have to stick to just one.
• Don't be afraid to write about something that would probably never happen. Science is the basis, but it is also fiction, so you can stray from the facts a bit. The bigger deal is to make your characters believable.
• Read a lot of sci-fi before you begin, just to get a feel for it. Some good role models for beginners are Madeline L'Engle, Garth Nix, Philip Pullman, Margaret Peterson Haddix, and James Patterson. (Note: Some of these authors write in other genres as well as science fiction). For more experienced readers, Frank Herbert,Eoin Colfer, Isaac Asimov, Arthur C. Clarke, Orson Scott Card, Steven Baxter and Robert A. Heinlein are suggested.
• Don't feel like you absolutely have to put it in the physical world we know. A lot of sci-fi has been successful within made-up worlds.

Warnings

• Many science fiction writers think that their main character has to be a scientific super-person. That's not true. Normal people are okay, too.
• Take inspiration from other writers, but don't steal their ideas. That might not be technically plagiarism, but after a while of one idea, it gets cliche. Avoid it.
• When you get writer's block, don't give up on the story. Give it some time. If you give up, you'll regret it later.