When I shoot using my 6x6 mf cameras, I always print square - even if it's a crop of the original neg size, i still crop to a square - it all makes so much sense to me. To compose the image, I walk around looking in the viewfinder until the motif looks correct, I dont consciously look at thirds or any other "rule" of composition. And strangely, when people have looked at my photographs, very rarely have they said "I wish this wasnt square" or "what a strange format".