Planning on writing the great American hard SF novel?  Here are a few essays that are required reading before you start.

First off, you may want to put alien civilizations into your opus.  But consider the relative likelihood of there actually being anyone else out there that we can contact.  Nick Bostrom hopes that the Mars probes find no life at all because if life existed on Mars, he argues, that means that creation of life is the easy part, and the reason we haven't run into advanced civilizations out there yet is because the real barrier to space colonization still lies in the future for us humans.

So assuming it's the creation of life in the first place that's the hard part (hence, no other intelligent species), maybe your story concerns humans reaching out and colonizing space themselves.  But here comes that old buzzkill Charlie Stross explaining that interstellar travel for humans is an incredibly, vastly unlikely endeavor, short of some sort of magic wand technology.

So maybe you decide to keep your story right here on Earth and focus more on artificial intelligence and a post-singularity world.  Well now you're really in trouble.  Do you even know what the singularity means?  It means the post-singularity world is, by definition, unpredictable!  We simply can't fathom what life will be like once computing power reaches a certain technological tipping point.

Crap.  I guess you should probably forget about your novel and just go back to watching BSG.