to my knowledge a cabinet has approx. four places where sound come out. where do you mic it? in front? in back? say you only had one mic. what would you do?
Start by listening around the speaker cabinet and finding the nicest sounding spot. Then start moving that mic. There is no formula that will work for every cabinet. You really have to place it, record and check the recording. Repeat that about ten times and you will be getting close.