Once I was in a store here in Mexico and the clerk asked me if I wanted a “canastilla”.  I didn’t know what she meant until she brought me a plastic shopping basket.  My Mexican friends laughed when I said that I would have understood “canastita”.  I still don’t know a rule for when to use -illa.  I do know that “ventanilla” is the word for the small airplane window so I’m guessing that in general the “-illa” suffix is used for physically small things and not for any of the other uses.

 But the suffix -it@ is used a lot.  “Cafecito” is a common word and there are even restaurants that are named “El Cafecito”.  A Spanish teacher once told me that the Mexicans used to use diminutives in order to set themselves apart from the Conquistadores, who made demanding, forceful requests.