Well, I have a number of tricks for writing stories. If you were to cross-check with Doitsujin, you'd find that I go into elaborate detail as to how things work, but the truth is that I won't use more than half of my theories in written text. But it's nice to know these theories in case you do need to go a little deeper than you originally planned.
To further this point, I shall start by mentioning the two biggest tricks I use in this area.
1) Capitalise on what others have done before.
People that don't know much about science will believe anything that is spoon fed to them if you make it SOUND realistic. What makes it even easier is going with popular ideas already made. I know scientific people that really believe the technology of Star Trek is possible. If you were to design scientific theories BASED on those particular existing ideas. People are even more likely to believe it than a reinforced model.
2) Don't explain what you don't need to.
This works REALLY well with first person stories. The example I used with Doitsujin I believe is something along the lines of "The Elandyl have mastered FTL travel, but stuffed If I know how it works. I translated the word 'quark' and the rest of it just went over my head."
Suddenly, it doesn't matter how the FTL drive works. It just does, but the character can't explain it. He's a diplomat with an interest in computers.
Using those two principals, I get away with blue murder. (metaphorically)
I've also recently realised exactly how important it is to have your story layed out in dot points before you start writing. I went back and did that and WOW, suddenly I know where I'm going.
Anyway, Hope I've been of some help.