When it comes to character creation, witch is one part that you should really know when it comes to how to write science fiction, I see that many people think that it is very hard, or it is very complex etc … But I will show you that in fact it is something easy, and that you can do it quickly.
When you start to create your characters keep in mind that you should always create a full story for them. Most people just do it as they write or just make some small notes about them, witch is totally wrong. The real power is in the story. Basically you should build a life for your character. You have to know what his childhood was like, what kind of parents he had ?, was he poor ?, was he rich? etc … I can keep going on an on about this. You might think that this is not necessary or that it is stupid to do, but let me tell you that it would help a lot more than you think when you actually start to write your science fiction.
You have to know all the details behind your character so you can write more detailed stuff about him and also you can even base a part of your main storyline on his story. This is a powerful technique that a lot of good writers use and it is a very successful one.
Another thing I recommend doing, is looking for real persons to inspire you. Like heroes and stuff like that. Do some research about some guy in real life, or in history and just adapt some of his life / story to your character. This technique will make your character a lot more "real", thus making the reader understand more about him and who he is.
Like I said above, character creation is a very important part when you want to know more about how to write science fiction.