Here's a question for the painters out there. 
I have always composed in rectangles and was warned, years ago, against square compostitions.  I notice, however, that the square is a very common format in the oil painting world.  Do any of you have any pointers for using the square format?  I have always used divisions of thirds in the rectangle format to provide general guidelines for emphasis placement.   Any thoughts?  Drop me a note or comment.  I'll be interested in hearing.   Thanks!