I have no standard method. Sometimes I crop, sometimes I don't. Many times, however, the print ends up more or less related to the film format. My 6x6 pictures are almost always cropped more square-ish than my 24x36. But sometimes my 24x36 negs end up as square prints, and sometimes I take a narrow strip of that 6x6 neg and make it a 1:3 panorama.
The available format definetly has its say in the way I compose, but when I return to the neg after a while I may see quite a different picture within that neg.
I'm not very helpful, am I?