Spent about 3 hours trying to figure out docking the other night (still pretty new at this). I was trying for something along the lines of Gemini 7/6A with two kerballed craft rendezvousing in orbit but actually docking, then return to Kerbin. Seven reverts in I finally get a perfect intercept, I'm approaching the target. 30m out, dead straight for the docking port when BANG! Staging. Off comes the RCS and SAS (ready for rentry) leaving the now unpowered control pod tumbling about. Of course, hadn't quicksaved at all. Bugger (and other selected swear words) Spen. the next half hour chasing it about with the other craft to see if I could rescue what-his-kerb from spending all eternity on orbit, either by docking and reentering or at least nudging him into a degrading orbit.
