|"[To] Jupiter and beyond the infinite"|
—2001: A Space Odyssey
To any hard sci-fi buffs out there, there is a great website that deals with scientifically accurate information about space exploration called Atomic Rockets. There you'll find information about building spaceships and space-stations; the logistics of space travel; life in space; colonization of space; space warfare; galactic world-building; etc. There are so much to read up on, and a great resource if you want to make a realistic sci-fi setting. It is worth checking out if you never been there.
Be forewarned: The harder the science of your sci-fi is, the more boring and mundane the setting is. In other words: You'll not get anything that made Star Wars so awesome; you'll only get the dullest parts of 2001: A Space Odyssey. Like any good sci-fi, there are workarounds, so don't get discouraged. ;)