1) NEVER change the grade on the spot - get the write-up/e-mail,
   and decide later. This way, we'll avoid rush decisions,
   inconsistencies in grading, etc.
2) of course, always be polite, eg.:
    - "I understand your argument, but, unfortunately,
       this was the general policy, for the whole class"
    - "you make a good point - we will give you <> extra points, since
       the answer was not perfect, but close to it"
3) RECORD: if you do give extra points, write down the details, for consistency
   (in case somebody else, with the same setting, asks for extra points)
4) CONTACT ME, for difficult cases