Plodding plotting

Plots!  Mine tend toward the cliched and been-there-done-that variety.  I seem to be unable to come up with fresh and exciting ideas on my own, but instead gravitate to pulling something out from the bottom of my brain that's been lying there since I read such-and-such book in the fourth grade, borrowing a little from another book in the mid-70's, with just a touch of another long-buried book thrown in for good measure.  Not on purpose, of course.  

I've tried to do all that I should:  sit down and think about the story, plot it out ahead of time, figure out the theme.  But once I start writing, I tend to stray away from that.  I usually end up with about 3 or 4 themes running around, enough backstory to fill 3 novels, not enough conflict, and a story that won't end.  I try to make my short stories do too much.  (Maybe I should move on to novels, but that's another story in itself)  Indecision is my nemesis, and when I can't decide, I freeze.  And so the stories languish.

Surely there's a foolproof, fast and furious method of plotting, right?  Someone out there has the answer, right?  

So how do you plot?  Which comes first?  The chicken/character, or the egg/plot?  What questions do you ask yourself in order to come up with your plot?  How much do you plot out/outline before you start writing?