What counts as "runway in sight" when flying an IFR approach to minimums? I've watched a few videos on youtube where the pilot flies an Instrument Landing System (ILS) approach to the minimum allowed altitude before establishing visibility of the runway (MDA or minimums).

What I'm wondering though is what constitutes "runway in sight"?  I mean, in some cases that's going to be obvious (ie., you can see the runway clear as day long before minimums.)  But what if the cloud base is right at minimum and you can kind of see outside, but not in every direction (ie. maybe it's slightly clearer just a bit to your left than to your right.)

What do you have to see to consider the runway in sight?  The whole runway?  Just the lights? Just the approach lights?  Just the VASI/PAPI?  Would it be considered enough if, perhaps, you could see a windsock that you know is close to the runway?  Or perhaps there's a cross street right before the runway that you're very familiar with, would that work?  What would be considered "runway in sight" so that you can continue the approach rather than going missed?



Note/Clarification: The general rule, of course, is "when in doubt, go missed".  So in a lot of ways this question is academic.  What I would love, though, is a two part answer, with one part that has the exact rules (per the FAA) and the other with some common sense guidance on when to continue and when to go missed.
From FAR 91.175:


  (3) Except for a Category II or Category III approach where any necessary visual reference requirements are specified by the Administrator, at least one of the following visual references for the intended runway is distinctly visible and identifiable to the pilot:
  
  (i) The approach light system, except that the pilot may not descend below 100 feet above the touchdown zone elevation using the approach lights as a reference unless the red terminating bars or the red side row bars are also distinctly visible and identifiable.
  
  (ii) The threshold.
  
  (iii) The threshold markings.
  
  (iv) The threshold lights.
  
  (v) The runway end identifier lights.
  
  (vi) The visual approach slope indicator.
  
  (vii) The touchdown zone or touchdown zone markings.
  
  (viii) The touchdown zone lights.
  
  (ix) The runway or runway markings.
  
  (x) The runway lights